Business Statistics.pdf

UNIT – 1
BUSINESS STATISTICS
What is Statistics?
The word “Statistics” has been derive from the Latin word “Status” or Italian word “Statista” or
German word “Statistika”. Each of these words means Political State. Initially, Statistics was
used to collect the information of the people of the state about their income, health, illiteracy and
wealth etc.
But now a day, Statistics has become an important subject having useful application in various
fields in day to day life.
Statistics in Plural Sense:--
In the plural sense, Statistics refers to information in terms of numbers or numerical data such as
Population Statistics, Employment Statistics etc. However any numerical information is not
statistics.
Example: Ram gets 100 per month as pocket allowance is not Statistics. It is neither an
aggregate nor an average. Whereas average pocket allowance of the students of Class X is 100
per month and there are 80 students in class XI & 8 students in Class XII are Statistics.
The following table shows a set of data that which is Statistics and which is not Statistics.
Data which are not Statistics Data which are Statistics
A cow has 4 legs. Average height of the 26 plus male people in
India is 6 feet compare to 5 feet in Nepal.
Ram has 200 rupees in his pocket. Birth rate in India is 18 per thousand compare
to 8 per thousand in USA.
A young lady was run over by a speeding truck
at 100 km per hour.
Over the past 10 years, India has won 60 test
matches in cricket and lost 50.
From above information we can say that “All Statistics are data, but all data are not
Statistics”
Definition:-
According to Bowley - “Statistics are numerical statements of facts in any department of
enquiry placed in relation to each other.”

According to Yule and Kendall ----- “By Statistics we mean quantitative data affected to
marked extent by multiplicity of causes.”
Characteristics of Statistics in Plural Sense
Main characteristics of Statistics in terms of numerical data are as follows:
(1) Aggregate of Facts – A single number does not constitute Statistics. We can not draw
any conclusion from single number. We can draw any conclusion by the aggregate
number of facts.
For example, if it is stated that there are 1,000 students in our college then it has no
significance. But if it is stated that there are 300 students in arts, 400 students in
commerce and 300 in science in our college. It makes statistical sense as this data convey
statistical information. Similarly if it is stated that population of India is 130 crore or the
value of total exports from India is 11, 66,439 crore then these aggregate of facts will be
termed as Statistics.
(2) Numerically Expressed - Statistics are expressed in terms of numbers. Qualitative
aspects like small or big, rich or poor etc. are not statistics. For instance if we say that
Irfan Pathan is tall Sachin is short then this statement has no statistical sense. However if
it is stated that height of Irfan Pathan is 6 ft and 2 inch and the height of Sachin is 5 ft and
4 inch then these numerical will be called Statistics.
(3) Affected by Multiplicity of Causes – Statistics are not affected by any single factor but
it is affected by many factors. For instance 30% rise in prices may have been due to
several causes like reduction in supply, increase in demand, shortage of power, rise in
wages, rise in taxes, etc.
(4) Reasonable Accuracy - A reasonable degree of accuracy must be kept in view while
collecting statistical data. This accuracy depends on the purpose of investigation, its
nature, size and available resources.
(5) Pre-determined Purpose - Statistics are collected with some pre-determined
objective. Any information collected without any definite purpose will only be a
numerical value and not Statistics. If data pertaining to the farmers of a village is
collected, there must be some pre-determined objective. Whether the statistics are
collected for the purpose of knowing their economic position or distribution of land
among them or their total population. All these objectives must be pre – determined.
(6) Collected in a Systematic Manner – Statistics should be collected in a systematic
manner. Before collecting the data, a plan must be prepared. No conclusion can be drawn
from data collected in haphazard manner. For instance, data regarding the marks secured
by the students of a college without any reference to the class, subject, examination, or
maximum marks, etc will lead no conclusion.

Statistics in Singular Sense
In a singular sense, statistics means science of statistics or statistical methods. It refers
to techniques or methods relating to collection, classification, presentation, analysis
and interpretation of quantitative data.
Definition
------ Statistics may be defined as the collection, presentation, analysis and interpretation
of numerical data. ------------------- CROXTON AND COWDEN
------Statistics is the science which deals with the collection, classification and tabulation
of numerical facts as a basis for the explanation, description and comparison of
phenomena. ------------------- LOVITT
Subject Matter of Statistics
Subject matter of statistics includes two components:
1. Descriptive Statistics 2. Inferential Statistics
1. Descriptive Statistics: Descriptive Statistics refers to those methods which are used
for the collection, presentation as well as analysis of data. These methods relate
measurement of central tendencies, measurement of dispersion, measurement of
correlation etc. For Example: Descriptive statistics is used when you estimate
average height of the secondary students in your school. Descriptive statistics is also
used when you find the marks in science and mathematics of the students in all
classes are intimately related to each other.
2. Inferential Statistics: Inferential Statistics refers to all such methods by which
conclusion are drawn related to the universe or population on the basis of a given
sample. For example: If your class teacher estimate average weight of the entire
class on the basis of average weight of only a sample of sample of students of the
class then we use the inferential statistics.
Important terminology in statistics
1. Population: By population we mean a well defined set or group of all the objects for a
particular study. The objects may be persons, plants, books, fishes in ponds, shops etc.
the population will consist of certain elements like the plants of a certain kind in a
specified field, the fishes in a pond, the unemployed person in India, books in library and
so on. For instance, if we want to study the properties of students in a school then the
population consists of all the students of school. For instance if we want to study about
the books in a library then the population includes all the books of the library etc. if the
number of elements are limited then the population is finite. On the other hand if the

number of elements is not limited then the population is infinite. Mostly we deal with
finite population.
2. Sample: It is a part of the population selected by some sampling procedure. The process
of selection of sample is known as sampling. The number of objects in the sample is
called the size of the sample. It is believed that a sample is best representative of the
population.
For instance, suppose a research worker is required to study the weight of fishes in a
pond after a particular period of growth. For this purpose suppose that there are 3,000
fishes in the pond, he may either measure the weight of all the fishes in the pond or he
may decide to select a small group of fishes and measure their weights. The first
approach of measuring the weight of all fishes is called complete enumeration or
census. Another approach in which only a small group of fishes is considered is called
sample survey. In brief we can say that in complete enumeration, information is
collected on all the units of the universe and in sample survey, only a part of the universe
is considered.
3. Variable: A property of objects is known as variable which differ from object to object
and is expressible numerically, in terms of numbers.
For instance: the marks in Mathematics of students in a class can be expressed in the
term of marks obtained by the students. So it is a variable property which is expressible
quantitatively.
4. Attribute: A property and characteristic of objects is known as attribute which are not
expressible quantatively in number. We can express the data qualitatively. For example,
smoking, color, honesty etc.
CHARACTERISTICS OF STATISTICS
1. Statistics are aggregate of facts.
2. Statistics are numerically expressed.
3. Statistics are affected to a marked extent by multiplicity of causes.
4. Statistics are either enumerated or estimated with reasonable standard of accuracy
5. Statistics are collected in a systematic manner.
6. Statistics are collected for a pre-determined purpose.
7. Statistics should be placed in relation to each other.
In the absence of the above characteristics numerical data can’t be called Statistics and hence “all
statistics are numerical statements of facts but all numerical statements of facts are not statistics.”
According to above Definitions, Statistics is both a science and an art. It is related to the
study and application of the principles and methods applicable in the collection,

presentation, analysis, interpretation and forecasting of data. Or statistical facts
influenced by several factors and related to any area of knowledge or research so that
concrete and intelligent decisions may be taken in the phase of uncertainty
NATURE OF STATISTICS
Statistics as a science: science refers to a systematized body of knowledge. It studies cause and
effect relationship and attempts to make generalizations in the form of scientific principles or laws.
“Science, in short, is like a light house that gives light to the ships to find out their own way but
doesn’t indicate the direction in which they should go.” Like other sciences, Statistical Methods are
also used to answer the questions like, how an investigation should be conducted. In what way the
valid and reliable conclusions can be drawn? Statistics is called the science of scientific methods.
In words of Croxton and Cowden, “Statistics is not a science, it is scientific
methods.”According to Tippet, “as science, the statistical method is a part of the general scientific
method and is based on the same fundamental ideas and processes.”
Statistics as an art: we know that science is a body of systematized knowledge. How this
knowledge is to be used for solving a problem is work of an art. An art is an applied knowledge. It
refers the skill of handling facts so as to achieve a given objective. It is concerned with ways and
means of presenting and handling data, making inferences logically and drawing relevant conclusion.
Art aspects of statistics tell, ‘how to use statistical rules and principles to study the problems and
finding their solutions. ‘Collections of statistics (data) its use and utility are itself an art.
Statistics is both science and art: After studying science and art aspects of statistics, it is used
not only to gain knowledge but also to understand the facts and draw important conclusions from it. If
science is knowledge, then art is action. Looking from this angle statistics may also be regarded as an
art. It involves the application of given methods to obtain facts, derive results and finally to use them
for devising action.
STAGES IN A STATISTICAL INVESTIGATION 5 stages -
1. Collection: This is the primary step in a statistical study and data should be collected
with care by the investigator. If data are faulty, the conclusions drawn can never be
reliable. The data may be available from existing published or unpublished sources or
Collection Organisation Presentation
Analysis Interpretation

else may be collected by the investigator himself. The first hand collection of data is one
of the most difficult and important tasks faced by a statistician.
2. Organization: Data collected from published sources are generally in organized form.
However, a large mass of figures that are collected from a survey frequently needs
organization. In organizing, there are 3 steps as
(A) Editing (B) Classify (C) Tabulation.
(A)Editing: The collected data must be editing very carefully so that the omissions,
inconsistencies irrelevant answers and wrong computation in the returns from a survey
may be corrected or adjusted.
(B)Classify: Classification is the process of arranging the data according to some common
characteristics possessed by the items constituting the data.
(C)Tabulation: To arrange the data in columns and rows.
Hence collected data is organized properly so that the desire information may be highlighted and
undesirable information avoided.
3. Presentation: Arranged data is not capable to influence a layman. Thus, it is necessary
that data may be presented with the help of tables, diagrams and graphs. By these devices
facts can be understood easily.
4. Analysis: A major part of it is developed to the methods used in analyzing the presented
data, mostly in a tabular form. For this analysis, a number of statistical tools are
available, such as averages, correlation, regression etc.
5. Interpretation: the interpretation of a data is a difficult task and necessitates a high
degree of skills and experience in the statistical investigation because certain decisions
made on the basis of conclusions drawn.
SCOPE OF STATISTICS
In early stages, the scope of statistics was very limited. It was confined mainly to the
administration of government and was, therefore, called the ‘Science of Kings’. But in modern time,
the scope of statistics has widened usually all those facts come in the purview of statistics, which are
expressed in quantitative terms directly or indirectly. That is why Croxton & Cowden observed,
“Today there is hardly a phase of endeavor which does not find statistical devices at least
occasionally useful.” It is not unfair to say, science without statistics bears no fruit and statistics
without science have no root.” The applications of statistics are so numerous that it is often
remarked, “Statistics is what statisticians do.” Now let us examine a few fields or areas in which
statistics is applied.

1. Statistics and the State: in recent years the functions of the state have increased
tremendously. The concept of the state has changed from that of simply maintaining law
and order to that of a welfare state. Statistical data and statistical methods are of great
help in promoting human welfare. The government in most countries is the biggest
collector and user of statistical data. These statistics help in framing suitable policies.
2. Statistics in Business and Management: with growing size and increasing competition,
the problems of business enterprises have become complex. Statistics is now considered
as an indispensable tool in the analysis of activities in the field of business, commerce
and industry. The object can be achieved by properly conducted market survey and
research which greatly depends on statistical methods. The trends in sales and production
can be determined by statistical methods like time-series analysis which are essential for
future planning of the phenomena. Statistical concepts and methods are also used in
controlling the quality of products to satisfaction of consumer and the producer. The
bankers use the objective analysis furnished by statistics and then temper their decisions
on the basis of qualitative information.
3. Statistics and Economics: R.A.Fisher complained of “the painful misapprehension that
statistics is a branch of economics.” Statistical Data and methods are of immense help in
the proper understanding of the economic problems and in the information of economic
policies. In the field of exchange, we study markets, law of prices based on supply and
demand, cost of production, banking and credit instruments etc. The development of
various economic theories own greatly to statistical methods, e.g., ‘Engel’s law of family
expenditure’, ‘Malthusian theory of population’. The impact of mathematics and statistics
has led to the development of new disciplines like ‘Econometrics’’ and ‘Economic
Statistics’. In fact, the concept of planning so vital for growth of nations would not have
been possible in the absence of data and proper statistical analysis.
4. Statistics and Psychology and Education: Statistics has found wide application in
psychology and education. Statistical methods are used to measure human ability such as;
intelligence, aptitude, personality, interest etc. by tests. Theory of learning is also based
on Statistical Principles. Applications of statistics in psychology and education have led
to the development of new discipline called ‘Psychometric’.
5. Statistics and Natural science; Statistical techniques have proved to be extremely useful
in the study of all natural sciences like biology, medicine, meteorology, botany etc. for
example- in diagnosing the correct disease the doctor has to rely heavily on factual data
like temperature of the body, pulse rate, B.P. etc. In botany- the study of plant life, one
has to rely heavily on statistics in conducting experiments about the plants, effect of
temperature, type of soil etc. In agriculture- statistical techniques like ‘analysis of
variance’ and ‘design of experiments’ are useful for isolating the role of manure, rainfall,
watering process, seed quality etc. In fact it is difficult to find any scientific activity
where statistical data and methods are not used.

6. Statistics and Physical Science: The physical sciences in which statistical methods were
first developed and applied. It seems to be making increasing use of statistics, especially
in astronomy, chemistry, engineering, geology, meteorology and certain branches of
physics.
7. Statistics and Research; statistics is indispensable in research work. Most of the
advancement in knowledge has taken place because of experiments conducted with the
help of statistical methods. Statistical methods also affect research in medicine and public
health. In fact, there is hardly any research work today that one can find complete without
statistical methods.
8. Statistics and Computer: The development of statistics has been closely related to the
evolution of electronic computing machinery. Statistics is a form of data processing a
way of converting data into information useful for decision-making. The computers can
process large amounts of data quickly and accurately. This is a great benefit to business
and other organizations that must maintain records of their operations. Processing of row
data is extensively required in the application of many statistical techniques.
CLASSIFICATION OF STATISTICS
Statistics can be divided into 3 parts;
1. Descriptive Statistics: Descriptive statistics is related to numerical data or facts. Such
data are collected either by counting or by some other process of measurement. It is also
related to those methods, includes editing of data, classification, tabulation, diagrammatic
or graphical presentation, measures of central tendency, measures of dispersion,
correlation etc., help to make the description of numerical facts simple, systematic,
synoptic understandable and meaningful.
2. Inferential Statistics: Inferential statistics help in making generalizations about the
population or universe on the basis of study of samples. It includes the process of
drawing proper and rational conclusion about the universe. Among these methods,
probability theory and different techniques of sampling test are important.
3. Applied Statistics; It involves application of statistical methods and techniques to the
problems and actual facts. For example-statistics related to national income, industrial
and agricultural production, population, price etc. are called applied statistics. It can be
divided into 2 parts-(1) Descriptive Applied Statistics- it deals with the study of the dat
DESCRIPTIVE STATISTICS
INFERENTIAL STATISTICS
APPLIED STATISTICS

which are known and which naturally relate. Its main object is to provide descriptive
information either to the past or to the present for any area. For example- price index
number and vital statistics comes under the category of descriptive applied statistics. (2)
Scientific Applied Statistics- under this branch of statistical science, statistical methods
are used to formulate and verify scientific laws. For example-an effort is made by an
economist to establish the law of demand, quantitative theory of money, trade circle etc.
These are established and verify by the help of scientific applied statistics.
IMPORTANCE OF STATISTICS
In recent days, we hear talking about statistics from a common person to highly qualified person.
It only show that how statistics has been intimately connected with wide range of activities in daily
life. They realize that work in their fields require some understanding of statistics. It indicates the
importance of the statistics. A.L.Bowley says, “Knowledge of statistics is like knowledge of foreign
language or of algebra. It may prove of use at any time under any circumstances”.
1. Importance to the State or Government; In modern era, the role of state has increased
and various governments of the world also take care of the welfare of its people.
Therefore, these governments require much greater information in the form of numerical
figures. Statistics are extensively used as a basis for government plans and policies. For
example-5-years plans are framed by using reliable statistical data of different segments
of life.
2. Importance in Human Behavior; Statistical methods viz., average, correlation etc. are
closely related with human activities and behavior. For example-when a layman wishes
to purchase some article, he first enquiries about its price at different shops in the market.
In other words, he collects data about the price of a particular article and aims at getting
idea about the average of the prices and the range within which the price vary. Thus, it
can be concluded that statistics play an important role in every aspect of human activities
and behavior.
3. Importance in Economics; Statistics is gaining an ever increasing importance in the
field of economics. That is why Tugwell said, “The science of economics is becoming
statistical in its method.” Statistics and economics are so interrelated to each other that
the new disciplines like econometrics and economic statistics have been developed.
Inductive method of generalization used in economics, is also based on statistical
principle. There are different segments of economics where statistics are used-
(A) Consumption- By the statistics of consumption we can find the way in which people in
different group spend their income. The law of demand and elasticity of demand in the field
of consumption are based on inductive or inferential statistics.
(B) Production- By the statistics of production supply is adjusted according to demand. We
can find out the capital invested in different productive units and its output. The decision

about what to produce, how much to produce, when to produce is based on facts analyzed
statistically.
(C) Distribution- Statistics play a vital role in the field of distribution. We calculate the
national income of a country by statistical methods and compare it with other countries. At
every step we require the help of figures without them. It is difficult to move and draw
inferences.
4. Importance in Planning; for the proper utilization of natural and manual resources,
statistics play a vital role. Planning is indispensable for achieving faster rate of growth
through the best use of a nation’s resources. Sometimes said that, “Planning without
statistics is a ship without rudder and compass.” For example- In India, a number of
organizations like national sample survey organization(N.S.S.O.), central statistical
organization (C.S.O.) are established to provide all types of information.
5. Importance in Business: The use of statistical methods in the solution of business
problems dates almost exclusively to the 20th
century. Or now days no business, large or
small, public or private, can prosper without the help of statistics. Statistics provides
necessary techniques to a businessman for the formulation of various policies and
planning with regard to his business. Such as-
(A) Marketing- In the field of marketing, it is necessary first to find out what can be sold
and them to evolve a suitable strategy so that goods reach the ultimate consumer. A
skillful analysis of data on population, purchasing power, habits of people, competition,
transportation cost etc. should precede any attempt to establish a new market.
(B) Quality Control- To earn the better price in a competitive market, it is necessary to
watch the quality of the product. Statistical techniques can also be used to control the
quality of the product manufactured by a firm. Such as - Showing the control chart.
(C) Banking and Insurance Companies- banks use statistical techniques to take
decisions regarding the average amount of cash needed each day to meet the
requirements of day to day transactions. Various policies of investment and sanction of
loans are also based on the analysis provided by statistics.
(D) Accounts writing and Auditing- Every business firm keeps accounts of its revenue
and expenditure. Statistical methods are also employed in accounting. In particular, the
auditing function makes frequent application of statistical sampling and estimation
procedures and the cost account uses regression analysis.
(E) Research and Development- Many business organizations have their own research
and development department which are responsible for collection of such data. These
departments also prepare charts groups and other statistical analysis for the purpose.
FUNCTIONS OF STATISTICS
Statistics performs the functions of making the numerical aspects of facts simple, precise,
comparable and reliable. In fact, the various functions performed by statistics are the basis of its

utility. R.W. Burgess says, “The fundamental gospel of statistics is to push back the domain of
ignorance, prejudice, rule of thumb, arbitrary and premature decisions, tradition & dogmatism and to
increase the domain in which decisions are made. Principles are formulated on the basis of analyzed
quantitative facts.”
1. Numerical and definite expression of facts: The first function of the statistics is the
collection and presentation of facts in numerical form. We know that the numerical
presentation helps in having a better understanding of the nature of a problem. One of the
most important functions of statistics is to present general statements in a precise and
definite form. Statements and facts conveyed in exact quantitative terms are always more
convincing than vague utterances.
2. Simplifies the data (condensation): Not only does statistics present facts in a definite
form but it also helps in condensing mass of data into a few significant figures. According
to A.E.Waugh, “the purpose of a statistical method is to simplify great bodies of
numerical data.”In fact, human mind cannot follow the huge, complex and scattered
numerical facts. So these facts are made simple and precise with the help of various
statistical methods like averages, dispersion, graphic or diagrammatic, presentation,
classification, tabulation etc. so that a common man also understand them easily.
3. Comparison of facts: Baddington states, “The essence of the statistics is not only
counting but also comparison.” The function of comparison does help in showing the
relative importance of data. For example- the pass % of examination result of a college
may be appreciated better when it is compared with the result of other college or the
results of previous years of the same college.
4. Establishment of relationship b/w two or more phenomena; to investigate the
relationship b/w two or more facts is the main function of statistics. For example-demand
and supply of a certain commodity, prices and wages, temperature and germination time
of seeds are interrelated.
5. Enlarges individual experiences: In word of Bowley, “the proper function of statistics
indeed is to enlarge individual experience.” Statistics is like a master key that is used to
solve problems of mankind in every field. It would not be exaggeration to say that many
fields of knowledge would have remained closed to the mankind forever but for the
efficient and useful techniques and methodology of the science of statistics.
6. Helps in the formulation of policies: statistics helps in formulating policies in different
fields, especially in economic, social and political fields. The government policies like
industrial policy, export-import policies, taxation policy and monetary policy are
determined on the basis of statistical data and their movements, plan targets are also fixed
with the help of data.
7. Helps in forecasting: statistical methods provide helpful means in estimating the
available facts and forecasting for future. Here Bowley’s statementis relevant that, “a
statistical estimate may be good or bad, accurate or the reverse; but in almost all cases it
is likely to be more accurate than a casual observer’s impression.”

8. Testing of hypothesis: statistical methods are also employed to test the hypothesis in
theory and discover newer theory. For example-the statement that average height of
students of college is 66 inches is a hypothesis. Here students of college constitute the
population. It is possible to test the validity of this statement by the use of statistical
techniques.
LIMITATIONS OF STATISTICS
Newsholme states, “Statistics must be regarded as an instrument of research of great value but
having several limitations which are not possible to overcome and as such they need out careful
attention.”
1. Statistics does not study qualitative facts: Statistics means aggregate of numerical
facts. It means that in statistics only those phenomena are studied which can be expressed
in numerical terms directly or indirectly. Such as- (1) directly in numerical terms like age,
weight and income of individual (2) no directly but indirectly like intelligent of students
and achievements of students (3) neither directly nor directly like morality, affection etc.
such type of facts don’t come under the scope of statistics.
2. Statistics doesn’t study individual: According to W.I.King, “Statistics from their very
nature of subject cannot and will never be able to take into account individual causes.
When these are important, other means must be used for their study.” These studied are
done to compare the general behavior of the group at different points of time or the
behavior of different groups at a particular point of time.
3. Statistical results are true only on the average: The statistical laws are not completely
true and accurate like the law of physics. For example – law of gravitational forces is
perfectly true & universal but statistical conclusions are not perfectly true. Such as the
average age of a person in India is 62 years. It does not mean that every person will attain
this age. On the basis of statistical methods we can say only in terms of probability and
not certainty.
4. Statistics as lack of complete accuracy: According to Conner, “Statistical data must
always be treated as approximations or estimates and not as precise measurements.”
Statistical result are based on sample or census data, are bound to be true only
approximately. For example – according to population census 2001, country’s population
is 1,02,70,15,247 but can real population may not be more or less by hundred, two
hundred and so on.
5. Statistics is liable to be misused: Statistical deals with figures and it can be easily
manipulated, distorted by the inexpert and unskilled persons it is very much likely to be
misused in most of the cases. In other words, the data should be handled by experts. Thus
it must be used by technically sound persons.

6. Statistics is only one of the methods of studying a phenomenon; According to Croxton
& Cowden, “It must not be assumed that the statistical method is the only method to be
used in research; neither this method be considered the best attack for every problem.”
The conclusions arrived at with the help of statistics must be supplemented with other
evidences.
7. Statistical results may be misleading; Without any reference, statistical results may
provide doubtful conclusions. For example – on the basis of increasing no. of prisoners in
the prison, it may be conclude that crime is increasing. But it may be possible that due to
rude behavior of police administration the number of prisoners is increasing but crime is
decreasing.
Therefore, it is worth-mentioning that every science based on certain assumption and limitations.
This does not reduce the importance of the subject but lays emphasis on the fact that precautions
should be taken while dealing with statistical analysis and interpretations.
DISTRUST OF STATISTICS
For practical view point statistics is very useful and important science. We know that utility of
statistics lies not merely in data but in correct analysis and proper interpretation of data. Several times
due to ignorance and bias, people misuse this delicate tool of knowledge and it creates distrust about
data.
Opinion about distrust of statistics;
1st
Opinion–Statisticians fully trust on the statistical conclusions because data is collected,
edited, analyzed and interpreted on the basis of statistical methods. Thus there is no reason to doubt
on it and said that “Figures don’t lie” or “Figures can prove nothing.”
2nd
Opinion –The statistics is looked upon with a suspicious eye and is quite often condemned
as “Figures are tissue of flesh hood. Discardi remarks that there are three kinds of lies- lies, damned
lies and statistics or “There are black lies, white lies, multi-chromatic lies and statistics is rainbow of
lies.”
Many persons feel that data are false, confusing and incorrect and with their help truth can be
proved wrong and lies can be put as truth. Hence it is said that “Statistics can prove anything” or
“Statistics are like clay of which you can make God or Devil, as you please.”
In this context, the observation is worth quoting that “Statistician is the person who is deeply
involved in statistical data. He can freely play with them, misuse them and can cheat common people.
So he is just magician who shows the games of tricks of hand through statistical data. His result can
be surprising but not trustworthy.

TYPES OF DATA
Data are the foundation stones and basic raw material in relation to any statistical investigation
that can be counted, classified, measured or quantified.
Types of Data are following;
ON THE BASIS OF CHARACTERISTICS OF FACTS
Data may be divided into two types;
1. Quantitative Data or Numerical Data: These types of data can be measured
directly such as age, income, production, marks etc. those facts are called variables
and variables may be discrete or continuous.
Discrete variable– Those variables whose values are individually distinct and discontinuous.
There is a definite difference between two variables. According to Boddington, “Discrete
variables is one where the variables (Individual values) differ from each other by definite

amounts.” For example – number of students of a class, number of children in a family, number
of cattle’s etc. It takes integral values such as 0, 1, 2, 3, 4 …etc.
Continuous variable – A continuous variable is one which assumes all values with in an
interval. That is no definite breaks are visible in this type of series. For example – age, weight,
height……
Questions; State which of the following represents Discrete data or Continuous data?
I. No. of accidents on each day in a month
II. Lengths of 1,000 bolts produced in a factory
III. Speed of an automobile in kilometer per hour
IV. No. of books on a library shelf
2. Qualitative Data or Categorical Data: They include data relating to such facts
which can‘t be measured directly but are counted or categorized to the basis of
attributes such as literates, illiterates, unemployed, honest etc. are called attributes.
For example- population can be classified on the basis of males and females or males
may be classified on the basis of marital status, i.e. married or unmarried. Qualitative
Data may further be classified into two categories
ON THE BASIS OF VARIABLES
On the basis of variables, also data may be of two types;
(1) Univariate Data: When the frequencies are determined on the basis of one variable. For
example – no. of workers on the basis of wages, no. of persons on the basis of age etc.
(2) Bivariate Data: When the data are edited or presented on the basis of two variables
simultaneously. For this two-way frequency table is constructed, one variable is placed
horizontally and the second one vertically. For example – to present the number of
students in one table on the basis of marks obtained in two subjects, to tabulate the no. of
persons in one table on the basis of two variables i.e. height and weight.
ON THE BASIS OF ARRANGEMENTS
Data may be categorized into two types;
(1) Raw Data: When the data is arranged and analyzed. It is called ‘Raw’ because it is
unprocessed by statistical methods.
(2) Arrange Data: When the data is processed and is arranged, summarized, classified and
tabulated in proper way.

Terms like ‘Data Point’ and ‘Data Set’ are also used in order to distinguish between the
numbers relating to individual or single facts and the aggregate of facts. For example– the
data of production of sugar for ten years will be termed as ‘Data Set’ and the figures for
production of one year will be as ‘Data Point’.
CLASSIFICATION
After collection and editing of data the first step towards further processing the same is classification.
Classification is a process in which the collected data are arranged in separate classes, groups or
subgroups according to their characteristics. According to Secrist, “Classification is the process of
arranging data into sequences and groups according to their common characteristics or separating
them into different classes.”
It concludes that classification means the arrangements and systematization of data into different
classes and these classes are determined on the basis of nature, objectives and scope of the enquiry.
OBJECTIVES OF CLASSIFICATION
Classification is a method or technique for extracting the essential information supplied by the raw
data.
(1) To condense the data: the main objective of classification is to condense and simplify the
statistical material, so that the same may be easily understandable.
(2) To bring out points of similarities and dissimilarities of data: classification brings out
clearly the points of similarity and dissimilarities of statistical facts because data of similar
characteristics are placed in one class i.e., males and females, literates and illiterates, married
and unmarried etc.
(3) To make facts comparable: by arranging the data according to the points of similarity and
dissimilarities, it helps in comparison.
(4) To bring out relationship: classification helps in finding cause and effect relationship in the
data. For example- based on literacy and criminal tendency of a group peoples, it can be
established whether literacy has any impact on criminal tendency or not.
(5) To prepare ground for tabulation: tabulation is the basis of statistical analysis and
classification is the basis for tabulation.
It concludes that classification occupies an important place in the process of statistical investigation.
The fact is that the process of tabulation, presentation and analysis can’t even be shorted without
classification.
CHARACTERISTICS OR RULES FOR A GOOD CLASSIFICATION
(1) Unambiguity: the various classes should be so defined that there is no roomfor doubt and
confusion. For example–population is classified as literates or illiterates.
(2) Exhaustive and mutually exclusive: classification should be so exhaustive (clear all aspects)
and one item may not be find place in more than one class. For example – students of a

college are classified into three groups – urban, rural and hostlers. This classification is not
mutually exclusive because among hostlers some may be urban and some other rural.
(3) Stability: the classification of data into various classes must be stable over be a period of time
of investigation.
(4) Suitability: the classification should confirm to the objectives of enquiry. For example–to study
the relationship between sex and university education, there is no need to classify on the basis
of age and religion.
(5) Flexibility: a good classification should be flexible so that adjustments may be easily be made
in classes according to changed situations. An ideal classification is one that can adjust itself
to these changes and yet retains its stability.
METHODS OF CLASSIFICATION
There are 4 methods of classification;
TABULATION
Tabulation is the next step of classification of the data and is designed to summaries lots of
information in a simple manner. In common language tabulation is the process of arranging data
in a systematic manner in the form of rows and columns. According to Blair, “Tabulation in its
broadest sense is any orderly arrangement of data in columns and rows.”
Geographical Classification
Chronological Classification
Qualitative Classification
Quantitative Classification

OBJECTIVES OF TABULATION
1. To simplify complex data
2. To facilitate comparison
3. To economies Space
4. To facilitate presentation
5. Help in analysis of data
6. To help in reference
DIFFERENCE BETWEEN CLASSIFICATION & TABULATION
Basis of Difference Classification Tabulation
Presentation Classifies into different
classes.
Classifies into row and columns.
Sequence First step Second step
Methods Method of statistical
Analysis.
Method of data Presentation
Use of data Original data are used. Derivatives like percentages, coefficients
Proportion, etc. may also be used.
FREQUENCY DISTRIBUTION
The tabular arrangement of data showing the frequency of each item is called a frequency
distribution. According to Croxton and Cowden, “Frequency distribution is a statistical table in
which different values of variable are shown in the sequence of magnitude along with
corresponding frequencies.”
TYPES OF FREQUENCY DISTRIBUTION
(1) Discrete frequency distribution: It is a discontinuous frequency distribution, where
observations are independent to each other. Each observation is different and separates
from others. Example – the no. of two children in 20 families;
1,1,2,3,4,3,2,1,1,4,5,2,4,2,2,1,3,3,2,5
Construction of discrete frequency distribution
1. A table with three columns is prepared.
2. In 1st
column of this table all possible values of the variable are placed.
3. In the 2nd
column, tally marks or tally bars are put, keeping in view the repetition of each
value.
4. After putting tally marks, they are counted and this counting is shown in the 3rd
column,
entitled frequency.

No. of
children
Tally Bars Frequency
1 |||| 5
2 |||| | 6
3 |||| 4
4 ||| 3
5 || 2
(2) Continuous frequency distribution: A continuous frequency distribution is such a
distribution in which data are arranged in classes or groups which are not exactly
measureable. Groups or class-intervals are always in a continuous form from the
beginning of the frequency distribution, till the end, within a given range of the data. For
example–
39,25,5,33,19,21,12,48,13,21,9,1,10,
9,8,12,17,40,12,46,37,17,27,30,6,2,23
Construction of continuous frequency distribution
(1) Find out the range = maximum marks – minimum marks
(2) Class size = decide the class size
(3) Width of class interval =
(4) Mid value =
(5) Class frequency = the no. of observations corresponding to a particular class is known
as frequency of the class.
Marks Tally Bars No. of
Students
0 – 10 |||||| 7
10 – 20 |||| ||| 8
20 – 30 |||| 5
30 – 40 |||| 4
40 – 50 ||| 3
There are two types of series according to class interval;

(1) Inclusive form; A frequency distribution in which each upper limit of each class is also
included. Such as; 0-9, 10-19, 20-29……………..
(2) Exclusive form; In which the upper limit of the next class-interval. Such as; 0-10, 10-20,
20-30…………

MEASURES OF CENTRAL TENDENCY
OBJECTIVES
After going through this unit, you will learn:
• the concept and significance of measures of central tendency
• to compute various measures of central tendency, such as arithmetic mean, median, mode and quartiles
• the relationship among various averages.
INTRODUCTION
The objective here is to find one representative value which can-be used to locate and summarise the
entire set of varying values. This one value can be used to make many decisions concerning the entire
set. We can define measures of central tendency (or location) to find some central value around which the
data tend to cluster.
SIGNIFICANCE OF MEASURES OF CENTRAI TENDENCY
Measures of central tendency i.e. condensing the mass of data in one single value , enable us to get an
idea of the entire data. For example, it is impossible to remember the individual incomes of millions of
earning people of India. But if the average income is obtained, we get one single value that represents the
entire population.
Measures of central tendency also enable us to compare two or more sets of data to facilitate comparison.
For example, the average sales figures of April may be compared with the sales figures of previous
months.
PROPERTIES OF A GOOD MEASURE OF CENTRAL TENDENCY
[1] It should be easy to understand and calculate.
[2] It should be rigidly defined.
[3] It should be based on all observations.
[4] It should be least affected by sampling fluctuation.
[5] It should be capable of further algebraic treatment.
[6] It should be least affected by extreme values.
[7] It should be calculated in case of open end interval.
Following are some of the important measures of central tendency which are commonly used in business
and industry.
 Arithmetic Mean
 Weighted Arithmetic Mean
 Median
 Quantiles(quartiles, deciles and percentiles)
 Mode
 Geometric Mean
 Harmonic Mean

ARITHMETIC MEAN
The arithmetic mean (or mean or average) is the most commonly used and readily understood measure of
central tendency. In statistics, the term average refers to any of the measures of central tendency.
Ungrouped data/Raw data
The arithmetic mean is defined as being equal to the sum of the numerical values of each and every
observation divided by the total number of observations. Symbolically, it can be represented as:
where,
∑X indicates the sum of the values of all the observations, and N is the total number of
observations.
For example, let us consider the monthly salary (Rs.) of 10 employees of a firm x
2500, 2700, 2400, 2300, 2550, 2650, 2750, 2450, 2600, 2400
If we compute the arithmetic mean, then 2500+2700+2400+2300+2550+2650+2750+2450+2600+2400 =
25300
Mean=25300 /10= Rs. 2530.
Therefore, the average monthly salary is Rs. 2530.
Discrete data
When the observations are classified into a frequency distribution, Therefore, for discrete data; the
arithmetic mean is defined as
Where, f is the frequency for corresponding variable x and N is the total frequency, i.e. N = f.
X f fx
10 12 120
20 23 460
30 35 1050
40 47 1880
50 38 1900
60 29 1740
70 16 1120
Sum 200 8270
Mean=8270/200= 41.35
=
=

Continuous Data
When the observations are classified into a frequency distribution, Therefore, for grouped data; the
arithmetic mean is defined as
Where X is midpoint of various classes, f is the frequency for corresponding class and N is the total
frequency, i.e. N = f.
This method is illustrated for the following data which relate to the monthly sales of 200 firms.
the midpoint of the class interval would be treated as the representative average value of that class.
Monthly Sales
(Rs. Thousand)
Mid point
X
No. of firms
f
fX
300-350 325 5 1625
350-400 375 14 5250
400-450 425 23 9775
450-500 475 50 23750
500-550 525 52 27300
550-600 575 25 14375
600-650 625 22 13750
650-700 675 7 4725
700-750 725 2 1450
Sum 200 10200
Mean=102000/200=510
MERITS OF MEAN
[1] It is easy to understand and calculate.
[2] It is rigidly defined.
[3] It is based on all observations.
[4] It is least affected by sampling fluctuation.
[5] It is capable of further algebraic treatment.
DEMERITS OF MEAN
1) It is highly affected by extreme values.
2) It is not calculated in case of open end interval.
=

MEDIAN
A second measure of central tendency is the median. Median is that value which divides the distribution
into two equal parts. Fifty per cent of the observations in the distribution are above the value of median and
other fifty per cent of the observations are below this value of median. The median is the value of the
middle observation when the series is arranged in order of size or magnitude (Ascending order).
UNGROUPED DATA
If the number of observations is odd, then the median is equal to one of the original observations (Middle).
For example, if the income of seven persons in rupees is 1100, 1200, 1350, 1500, 1550, 1600, 1800, then
Median = =4th
value
Median =1500
If the number of observations is even, then the median is the arithmetic mean of the two middle
observations.
For example, if the income of eight persons in rupees is 1100, 1200, 1350, 1500, 1550, 1600, 1800,1850,
then the median income of eight persons would be 1500+1550/2= 1525
DISCRETE SERIES
First we find cumulative frequency.then locate (N+1/2) the value in cumulative frequency.corresponding
that value of x is median.
X f cf
10 12 12
20 23 35
30 35 70
40 47 117
50 38 155
60 29 184
70 16 200
Sum 200
N=200
N+1/2=100.5
Median= 40
Median = th value
Median = th value

CONTINUOUS DATA
For continuous data, First we find cumulative frequency. then locate (N+1/2) the value in cumulative
frequency. corresponding class interval is median class.the following formula may be used to locate the
value of median.
where l1 is the lower limit of the median class, cf is the preceding cumulative frequency to the median class,
f is the frequency of the median class and h is the width of the median class.
Consider the following data which relate to the age distribution of 1000 workers in an industrial
establishment.
The location of median value is facilitated by the use of a cumulative frequency distribution as shown
below in the table.
Age (Years) No. of workers
f
Cumulative frequency
c.f
Below 25 120 120
25-30 125 245
30-35 180 425(cf)
35-40 160(f) 585
40-45 150 735
45-50 140 875
50-55 100 975
55 and Above 25 1000
N=1000
Median Class=(1000+1)/2=500.5th
=(35-40)
l1 =35,cf =425,f=160,N/2=500,h=5
Median =35+{(500-425)*5}/160 =35+375/160=35+2.34=37.34
MERITS OF MEDIAN
[2] It is rigidly defined.
[3] It is not affected by extreme values.
[4] It is calculated in case of open end interval.
[5] It is located by graphically also.
DEMERITS OF MEDIAN
[1] It is not based on all observations.
[2] It is affected by sampling fluctuation.
[3] It is not capable of further algebraic treatment.
Median=l1+ {(N/2 cf)*h} /f

MODE
The mode is the typical or commonly observed value in a set of data. It is defined as the value
which occurs most often or with the greatest frequency. The dictionary meaning of the term mode is most
usual'.
For example, in the series of numbers 3, 4, 5, 5, 6, 7, 8, 8, 8, 9, the mode is 8 because it occurs the
maximum number of times. That means in ungrouped data mode can find by inspection only.
DISCRETE DATA
Mode is the value of X which has highest frequency.
For example,
X f
10 12
20 23
30 35
40 47
50 38
60 29
70 16
Sum 200
Mode=40
CONTINUOUS DATA
First, we find Modal class = corresponding to highest frequency.
where l1 is lower limit of the modal class, f1
is the frequency of the modal class,f0 the frequency of the
preceding class, f2
is the frequency of the succeeding class, h is the size of the modal class.
To illustrate the computation of mode, let us consider the following data.
f
Below 25 120
25-30 125(f0)
30-35 180(f1)
35-40 160(f2)
40-45 150
45-50 140
50-55 100
55 and Above 25
Modal class=(30-35)
l1 =30, f1 =180, f0 =125, f2 =160,h=5
MODE = l1+ { }*h

Mode =30+{(180-125)/(2*180-125-160)}*5 =30+(55/75)*5 =30+3.667=33.67
MERITS OF MODE
[2] It is not affected by extreme values.
[3] It is calculated in case of open end interval.
[4] It is located by graphically also.
DEMERITS OF MODE
[1] It is not based on all observations.
[2] It is highly affected by sampling fluctuation.
[3] It is not capable of further algebraic treatment
[4] It is not rigidly defined.
RELATIONSHIP AMONG MEAN, MEDIAN AND MODE
MODE = 3MEDIAN-2 MEAN
QUARTILES
Quartiles are those values which divide the total data into four equal parts. Since three points divide the
distribution into four equal parts, we shall have three quartiles. Let us call them Q1, Q2, and Q3. The first
quartile, Q1, is the value such that 25% of the observations are smaller and 75% of the observations are
larger. The second quartile, Q2, is the median, i.e., 50% of the observations are smaller and 50% are
larger. The third quartile, Q3, is the value such that 75% of the observations are smaller and 25% of the
observations are larger.
UNGROUPED DATA
If the number of observations is odd, then the median is equal to one of the original observations (Middle).
For example, if the income of seven persons in rupees is 1100, 1200, 1350, 1500, 1550, 1600, 1800,1850
then
Q1 = =2.25nd
value
Q1=1200+0.25(1350-1200) =1200+37.5 =1237.5
Q3= =6.75th
value
Q3= 1600+.75(1800-1600) =1600+150 = 1750
DISCRETE SERIES
Q1= th value
Q3= th value

First we find cumulative frequency. then locate (N+1/4 ) and 3(N+1/4)the value in cumulative frequency
.corresponding that value of x is Q1 and Q2 respectively.
X f cf
10 12 12
20 23 35
30 35 70
40 47 117
50 38 155
60 29 184
70 16 200
Sum 200
N=200
Q1=N+1/4=50.25th
value
Q1 = 30
Q3 =3*(N+1/4)= 150.75th
value
Q3=50
CONTINUOUS DATA
For continuous data, First we find cumulative frequency. then locate (N+1/4) and 3(N+1/4)the value in
cumulative frequency. corresponding class interval is first quartile class and third quartile class
respectively.the following formula may be used to locate the value of quartiles.
where l1 is the lower limit of the first quartile class, cf is the preceding cumulative frequency to the first
quartile class, f is the frequency of first quartile class and h is the width of the first quartile class .
where l1 is the lower limit of the third quartile class, cf is the preceding cumulative frequency to the third
quartile class, f is the frequency of third quartile class and h is the width of the third quartile class .
Consider the following data which relate to the age distribution of 1000 workers in an industrial
establishment.
The location of quartile value is facilitated by the use of a cumulative frequency distribution as shown
below in the table.
f
Cumulative frequency
c.f
Below 25 120 120
25-30 125 245
30-35 180 425(cf)
35-40 160(f) 585
40-45 150 735
45-50 140 875
50-55 100 975
55 and Above 25 1000
Q1=l1+ {(N/4 cf)*h} /f
Q3=l1+ {(3N/4 cf)*h} /f
First
quartile
class
Third
quartile
class
Third
quartile
First
quartile

N=1000
Q1=(1000+1)/4=250.25th
=(25-30)
l1 =25,cf =120,f=125,N/4=250,h=5
Q1=25+{(250-120)*5}/125 =35+390/125=35+3.12=38.12
Q3=3(1000+1)/4=750.75th
=(45-50)
l1 =45,cf =735,f=140,3N/4=750,h=5
Q3=45+{(750-735)*5}/140=45+75/140=45+0.53=45.53
1] Following is the cumulative frequency distribution of preferred length of study-table obtained from
the preference study of 50 students.
A manufacturer has to take decision on the length of study-table to manufacture. What length would
you recommend and why?
2]An incomplete distribution of daily sales (Rs. thousand) is given below. The data relate to 229 days.
Daily sales No. of days Daily sales No. of days
(Rs. thousand) (Rs. thousand)
10-20 12 50-60 ?
20-30 30 60-70 25
30-40 ? 70-80 18
You are told that the median value is 46. Using the median formula, fill up the missing frequencies and
calculate the arithmetic mean of the completed data.

As the summer heat rises, hill
stations, are crowded with more and
more visitors. Ice-cream sales become
more brisk. Thus, the temperature is
related to number of visitors and sale
of ice-creams. Similarly, as the supply
of tomatoes increases in your local
mandi, its price drops. When the local
harvest starts reaching the market,
the price of tomatoes drops from a
princely Rs 40 per kg to Rs 4 per kg or
even less. Thus supply is related to
price. Correlation analysis is a means
for examining such relationships
systematically. It deals with questions
such as:
• Is there any relationship between
two variables?
Correlation
7
1. INTRODUCTION
In previous chapters you have learnt
how to construct summary measures
out of a mass of data and changes
among similar variables. Now you will
learn how to examine the relationship
between two variables.
Studying this chapter should
enable you to:
• understand the meaning of the
term correlation;
• understand the nature of
relationship between two
variables;
• calculate the different measures
of correlation;
• analyse the degree and direction
of the relationships.
CHAPTER
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92 STATISTICS FOR ECONOMICS
• If the value of one variable
changes, does the value of the
other also change?
• Do both the variables move in the
same direction?
• How strong is the relationship?
2. TYPES OF RELATIONSHIP
Let us look at various types of
relationship. The relation between
movements in quantity demanded
and the price of a commodity is an
integral part of the theory of demand,
which you will study in Class XII. Low
agricultural productivity is related to
low rainfall. Such examples of
relationship may be given a cause and
effect interpretation. Others may be just
coincidence. The relation between the
arrival of migratory birds in a
sanctuary and the birth rates in the
locality cannot be given any cause and
effect interpretation. The relationships
are simple coincidence. The
relationship between size of the
shoes and money in your pocket is
another such example. Even if
relationship exist, they are difficult
to explain it.
In another instance a third
variable’s impact on two variables
may give rise to a relation between the
two variables. Brisk sale of ice-creams
may be related to higher number of
deaths due to drowning. The victims
are not drowned due to eating of ice-
creams. Rising temperature leads to
brisk sale of ice-creams. Moreover, large
number of people start going to
swimming pools to beat the heat. This
might have raised the number of deaths
by drowning. Thus temperature is
behind the high correlation between
the sale of ice-creams and deaths due
to drowning.
What Does Correlation Measure?
Correlation studies and measures
the direction and intensity of
relationship among variables.
Correlation measures covariation, not
causation. Correlation should never be
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CORRELATION 93
interpreted as implying cause and
effect relation. The presence of
correlation between two variables X
and Y simply means that when the
value of one variable is found to change
in one direction, the value of the other
variable is found to change either in the
same direction (i.e. positive change) or
in the opposite direction (i.e. negative
change), but in a definite way. For
simplicity we assume here that the
correlation, if it exists, is linear, i.e. the
relative movement of the two variables
can be represented by drawing a
straight line on graph paper.
Types of Correlation
Correlation is commonly classified
into negative and positive
correlation. The correlation is said to
be positive when the variables move
together in the same direction. When
the income rises, consumption also
rises. When income falls,
consumption also falls. Sale of ice-
cream and temperature move in the
same direction. The correlation is
negative when they move in opposite
directions. When the price of apples
falls its demand increases. When the
prices rise its demand decreases.
When you spend more time in
studying, chances of your failing
decline. When you spend less hours
in your studies, chances of scoring
low marks/grades increase. These
are instances of negative correlation.
The variables move in opposite
direction.
3. TECHNIQUES FOR MEASURING
CORRELATION
Three important statistical tools used
to measure correlation are scatter
diagrams, Karl Pearson’s coefficient of
correlation and Spearman’s rank
correlation.
A scatter diagram visually
presents the nature of association
without giving any specific
numerical value. A numerical
measure of linear relationship
between two variables is given by
Karl Pearson’s coefficient of
correlation. A relationship is said to
be linear if it can be represented
by a straight line. Spearman’s
coefficient of correlation measures
the linear association between ranks
assigned to indiviual items according
to their attributes. Attributes are
those variables which cannot be
numerically measured such as
intelligence of people, physical
appearance, honesty, etc.
Scatter Diagram
A scatter diagram is a useful
technique for visually examining the
form of relationship, without
calculating any numerical value. In
this technique, the values of the two
variables are plotted as points on a
graph paper. From a scatter diagram,
one can get a fairly good idea of the
nature of relationship. In a scatter
diagram the degree of closeness of the
scatter points and their overall direction
enable us to examine the relation-
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ship. If all the points lie on a line, the
correlation is perfect and is said to be
unity. If the scatter points are widely
dispersed around the line, the
correlation is low. The correlation is
said to be linear if the scatter points lie
near a line or on a line.
Scatter diagrams spanning over
Fig. 7.1 to Fig. 7.5 give us an idea of
the relationship between two
variables. Fig. 7.1 shows a scatter
around an upward rising line
indicating the movement of the
variables in the same direction. When
X rises Y will also rise. This is positive
correlation. In Fig. 7.2 the points are
found to be scattered around a
downward sloping line. This time the
variables move in opposite directions.
When X rises Y falls and vice versa.
This is negative correlation. In Fig.7.3
there is no upward rising or downward
sloping line around which the points
are scattered. This is an example of
no correlation. In Fig. 7.4 and Fig. 7.5
the points are no longer scattered
around an upward rising or downward
falling line. The points themselves are
on the lines. This is referred to as
perfect positive correlation and perfect
negative correlation respectively.
Activity
• Collect data on height, weight
and marks scored by students
in your class in any two subjects
in class X. Draw the scatter
diagram of these variables taking
two at a time. What type of
relationship do you find?
A careful observation of the scatter
diagram gives an idea of the nature
and intensity of the relationship.
Karl Pearson’s Coefficient of
Correlation
This is also known as product moment
correlation and simple correlation
coefficient. It gives a precise numerical
value of the degree of linear
relationship between two variables X
and Y. The linear relationship may be
given by
Y = a + bX
This type of relation may be
described by a straight line. The
intercept that the line makes on the
Y-axis is given by a and the slope of
the line is given by b. It gives the
change in the value of Y for very small
change in the value of X. On the other
hand, if the relation cannot be
represented by a straight line as in
Y = X2
the value of the coefficient will be zero.
It clearly shows that zero correlation
need not mean absence of any type
of relation between the two variables.
Let X1
, X2
, ..., XN
be N values of X
and Y1, Y2 ,..., YN be the corresponding
values of Y. In the subsequent
presentations the subscripts
indicating the unit are dropped for the
sake of simplicity. The arithmetic
means of X and Y are defined as
X
X
N
Y
Y
N
= =
Σ Σ
;
and their variances are as follows
σ2
2 2
2
x
X X
N
X
N
X
=
−
= −
Σ Σ
( )
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and σ2
2 2
2
y
Y Y
N
Y
N
Y
=
−
= −
Σ Σ
( )
The standard deviations of X and
Y respectively are the positive square
roots of their variances. Covariance of
X and Y is defined as
Cov(X,Y) =
− −
=
Σ Σ
( )( )
X X Y Y
N
xy
N
Where x X X
= − and y Y Y
= −
are the deviations of the ith
value of X
and Y from their mean values
respectively.
The sign of covariance between X
and Y determines the sign of the
correlation coefficient. The standard
deviations are always positive. If the
covariance is zero, the correlation
coefficient is always zero. The product
moment correlation or the Karl
Pearson’s measure of correlation is
given by
r xy
N x y
= Σ
σ σ ...(1)
or
r
X X Y Y
X X Y Y
=
− −
− −
Σ
Σ Σ
( ) ( )
( ) ( )
2 2
...(2)
or
r
XY
X Y
N
X
X
N
Y
Y
N
=
−
− −
Σ
Σ Σ
Σ
Σ
Σ
Σ
( )( )
( ) ( )
2
2
2
2
...(3)
or
1 1 1 1
2 34 5 6 376 47
8
2 3 5 6 37 2 4 5 6 47
1 2 2
3
1 1 4 1 1 ...(4)
Properties of Correlation Coefficient
Let us now discuss the properties of the
correlation coefficient
• r has no unit. It is a pure number.
It means units of measurement are
not part of r. r between height in
feet and weight in kilograms, for
instance, could be say 0.7.
• A negative value of r indicates an
inverse relation. A change in one
variable is associated with change
in the other variable in the
opposite direction. When price of
a commodity rises, its demand
falls. When the rate of interest
rises the demand for funds also
falls. It is because now funds have
become costlier.
• If r is positive the two variables
move in the same direction. When
the price of coffee, a substitute of
tea, rises the demand for tea also
rises. Improvement in irrigation
facilities is associated with higher
yield. When temperature rises the
sale of ice-creams becomes brisk.
2015-16

CORRELATION 97
• The value of the correlation
coefficient lies between minus one
and plus one, –1 5 r 5 1. If, in any
exercise, the value of r is outside
this range it indicates error in
calculation.
• If r = 0 the two variables are
uncorrelated. There is no linear
relation between them. However
other types of relation may be there.
• If r = 1 or r = –1 the correlation is
perfect. The relation between them
is exact.
• A high value of r indicates strong
linear relationship. Its value is said
to be high when it is close to
+1 or –1.
• A low value of r indicates a weak
linear relation. Its value is said to
be low when it is close to zero.
• The magnitude of r is unaffected by
the change of origin and change of
scale. Given two variables X and Y
let us define two new variables.
U =
X – A
B
;V =
Y – C
D
where A and C are assumed means of
X and Y respectively. B and D are
common factors and of same sign. Then
rxy
= ruv
This. property is used to calculate
correlation coefficient in a highly
simplified manner, as in the step
deviation method.
As you have read in chapter 1, the
statistical methods are no substitute for
common sense. Here, is another
example, which highlights the need for
understanding the data properly
before correlation is calculated and
interpreted. An epidemic spreads in
some villages and the government
sends a team of doctors to the affected
villages. The correlation between the
number of deaths and the number of
doctors sent to the villages is found to
be positive. Normally the health care
facilities provided by the doctors are
expected to reduce the number of
deaths showing a negative correlation.
This happened due to other reasons.
The data relate to a specific time period.
Many of the reported deaths could be
terminal cases where the doctors
could do little. Moreover, the benefit
of the presence of doctors becomes
visible only after some time. It is also
possible that the reported deaths are
not due to the epidemic. A tsunami
suddenly hits the state and death toll
rises.
Let us illustrate the calculation of
r by examining the relationship
between years of schooling of farmers
and the annual yield per acre.
Example 1
No. of years Annual yield per
of schooling acre in ’000 (Rs)
of farmers
0 4
2 4
4 6
6 10
8 10
10 8
12 7
Formula 1 needs the value of
Σxy x y
, ,
σ σ
2015-16

From Table 7.1 we get,
Σ
Σ
xy
X X
N
x
=
=
−
=
42
112
7
2
,
( )
,
σ
σy
Y Y
N
=
−
=
Σ( )2 38
7
Substituting these values in
formula (1)
r = =
42
7
112
7
38
7
0 644
.
The same value can be obtained
from formula (2) also.
r
X X Y Y
X X Y Y
=
− −
− −
Σ
Σ Σ
( )( )
( ) ( )
2 2 ...(2)
r = =
42
112 38
0 644
.
Thus years of education of farmers
and annual yield per acre are
positively correlated. The value of r is
also large. It implies that more the
number of years farmers invest in
education, higher will be the yield per
acre. It underlines the importance of
farmers’ education.
To use formula (3)
r
XY
X Y
N
X
X
N
Y
Y
N
=
−
− −
Σ
Σ Σ
Σ
Σ
Σ
Σ
( )( )
( ) ( )
2
2
2
2
...(3)
the value of the following expressions
have to be calculated i.e.
Σ Σ Σ
XY X Y
, , .
2 2
Now apply formula (3) to get the
value of r.
Let us know the interpretation of
different values of r. The correlation
coefficient between marks secured in
English and Statistics is, say, 0.1. It
means that though the marks secured
in the two subjects are positively
correlated, the strength of the
relationship is weak. Students with high
marks in English may be getting
relatively low marks in statistics. Had
the value of r been, say, 0.9, students
with high marks in English will
invariably get high marks in Statistics.
TABLE 7.1
Calculation of r between years of schooling of farmers and annual yield
Years of (X– X ) (X– X )2
Annual yield (Y– Y ) (Y– Y )2
(X– X )(Y– Y )
Education per acre in ’000 Rs
(X) (Y)
0 –6 36 4 –3 9 18
2 –4 16 4 –3 9 12
4 –2 4 6 –1 1 2
6 0 0 10 3 9 0
8 2 4 10 3 9 6
1 0 4 16 8 1 1 4
12 6 36 7 0 0 0
Σ X=42 Σ (X– X )2
=112 Σ Y=49 Σ (Y– Y )2
=38 Σ (X–X )(Y– Y )=42
2015-16

CORRELATION 99
An example of negative correlation
is the relation between arrival of
vegetables in the local mandi and price
of vegetables. If r is –0.9, vegetable
supply in the local mandi will be
accompanied by lower price of
vegetables. Had it been –0.1 large
vegetable supply will be accompanied
by lower price, not as low as the price,
when r is –0.9. The extent of price fall
depends on the absolute value of r.
Had it been zero there would have
been no fall in price, even after large
supplies in the market. This is also
a possibility if the increase in supply
is taken care of by a good transport
network transferring it to other
markets.
Activity
• Look at the following table.
Calculate r between annual
growth of national income at
current price and the Gross
Domestic Saving as percentage
of GDP.
Step deviation method to calculate
correlation coefficient.
When the values of the variables
are large, the burden of calculation
can be considerably reduced by
using a property of r. It is that r is
independent of change in origin and
scale. It is also known as step
deviation method. It involves the
TABLE 7.2
Year Annual growth Gross Domestic
of National Saving as
Income percentage of GDP
1992–93 14 24
1993–94 17 23
1994–95 18 26
1995–96 17 27
1996–97 16 25
1997–98 12 25
1998–99 16 23
1999–00 11 25
2000–01 8 24
2001–02 10 23
Source: Economic Survey, (2004–05) Pg. 8,9
transformation of the variables X and
Y as follows:
U =
X – A
h
V =
Y – B
k
;
where A and B are assumed means, h
and k are common factors and have
same signs.
Then rUV
= rXY
This can be illustrated with the
exercise of analysing the correlation
between price index and money
supply.
Example 2
Price 120 150 190 220 230
index (X)
Money 1800 2000 2500 2700 3000
supply
in Rs crores (Y)
The simplification, using step
deviation method is illustrated below.
Let A = 100; h = 10; B = 1700 and
k = 100
2015-16

The table of transformed variables
is as follows:
Calculation of r between price index
and money supply using step deviation
method
TABLE 7.3
U V
X −






100
10
Y −






1700
100
U2
V2
UV
2 1 4 1 2
5 3 25 9 15
9 8 81 64 72
12 10 144 100 120
13 13 169 169 169
SU = 41; SU = 35; SU2
= 423;
SV2
= 343; SUV = 378
Substituting these values in formula (3)
r=
Σ
Σ Σ
Σ
Σ
Σ
Σ
UV
U U
U
U
V
V
2 2
−
( )( )
−
( )
−
( )
N
N N
2 2 (3)
=
−
×
− −
378
41 35
5
423
41
5
343
35
5
2 2
( ) ( )
= 0.98
The strong positive correlation
between price index and money
supply is an important premise of
monetary policy. When the money
supply grows the price index also rises.
Activity
• Using data related to India’s
population and national income,
calculate the correlation
between them using step
deviation method.
Spearman’s rank correlation
Spearman’s rank correlation was
developed by the British psychologist
C.E. Spearman. It is used when the
variables cannot be measured
meaningfully as in the case of price,
income, weight etc. Ranking may be
more meaningful when the
measurements of variables are suspect.
Consider the situation where we are
required to calculate the correlation
between height and weight of students
in a remote village. Neither measuring
rods nor weighing scales are available.
The students can be easily ranked in
terms of height and weight without
using measuring rods and weighing
scales.
There are also situations when you
are required to quantify qualities such
as fairness, honesty etc. Ranking may
be a better alternative to quantifica-
tion of qualities. Moreover, sometimes
the correlation coefficient between two
variables with extreme values may be
quite different from the coefficient
without the extreme values. Under
these circumstances rank correlation
provides a better alternative to simple
correlation.
Rank correlation coefficient and
simple correlation coefficient have the
same interpretation. Its formula has
2015-16

CORRELATION 101
been derived from simple correlation
coefficient where individual values have
been replaced by ranks. These ranks
are used for the calculation of
correlation. This coefficient provides
a measure of linear association between
ranks assigned to these units, not their
values. It is the Product Moment
Correlation between the ranks. Its
formula is
...(4)
where n is the number of observations
and D the deviation of ranks assigned
to a variable from those assigned to
the other variable. When the ranks are
repeated the formula is
rs = 1–
6
12 12
1
2
3
1 1
3
2 2
2
ΣD
m m m m
n n
+
−
+
−
+






−
( ) ( )
...
( )
where m1
, m2
, ..., are the number of
repetitions of ranks and
m m
3
1 1
12
...,
their corresponding corr ection
factors. This correction is needed for
every repeated value of both variables.
If three values are repeated, there will
be a correction for each value. Every
time m1 indicates the number of times
a value is repeated.
All the properties of the simple
correlation coefficient are applicable
here. Like the Pearsonian Coefficient
of correlation it lies between 1 and
–1. However, generally it is not as
accurate as the ordinary method.
This is due the fact that all the
information concerning the data is
not utilised. The first differences of
the values of items in the series,
arranged in order of magnitude, are
almost never constant. Usually the
data cluster around the central
values with smaller differences in the
middle of the array. If the first
differences were constant, then r and
rk
would give identical results. The
first difference is the difference of
consecutive values. Rank
correlation is preferred to Pearsonian
coefficient when extreme values are
present. In general
rk is less than or equal to r.
The calculation of rank correlation
will be illustrated under three
situations.
1. The ranks are given.
2. The ranks are not given. They have
to be worked out from the data.
3. Ranks are repeated.
Case 1: When the ranks are given
Example 3
Five persons are assessed by three
judges in a beauty contest. We have
to find out which pair of judges has
the nearest approach to common
perception of beauty.
Competitors
Judge 1 2 3 4 5
A 1 2 3 4 5
B 2 4 1 5 3
C 1 3 5 2 4
There are 3 pairs of judges
necessitating calculation of rank
correlation thrice. Formula (4) will be
used.
2015-16

r
D
n n
s = −
−
1
6 2
3
Σ
...(4)
The rank correlation between A and
B is calculated as follows:
A B D D2
1 2 –1 1
2 4 –2 4
3 1 2 4
4 5 –1 1
5 3 2 4
Total 14
formula (4)
r
D
n n
s = −
−
1
6 2
3
Σ
...(4)
= −
×
−
= − = − =
1
6 14
5 5
1
84
120
1 0 7 0 3
3
. .
The rank correlation between A
and C is calculated as follows:
A C D D2
1 1 0 0
2 3 –1 1
3 5 –2 4
4 2 2 4
5 4 1 1
Total 10
formula (4) the rank correlation is 0.5.
Similarly, the rank correlation
between the rankings of judges B and
C is 0.9. Thus, the perceptions of
judges A and C are the closest. Judges
B and C have very different tastes.
Case 2: When the ranks are not given
Example 4
We are given the percentage of marks,
secured by 5 students in Economics
and Statistics. Then the ranking has
to be worked out and the rank
correlation is to be calculated.
Student Marks in Marks in
Statistics Economics
(X) (Y)
A 85 60
B 60 48
C 55 49
D 65 50
E 75 55
Student Ranking in Ranking in
Statistics Economics
(Rx
) (RY
)
A 1 1
B 4 5
C 5 4
D 3 3
E 2 2
Once the ranking is complete
formula (4) is used to calculate rank
correlation.
Case 3: When the ranks are repeated
Example 5
The values of X and Y are given as
X 25 45 35 40 15 19 35 42
Y 55 60 30 35 40 42 36 48
In order to work out the rank
correlation, the ranks of the values
are worked out. Common ranks are
given to the repeated items. The
2015-16

CORRELATION 103
common rank is the mean of the ranks
which those items would have assumed
if they were slightly different from each
other. The next item will be assigned
the rank next to the rank already
assumed. The formula of Spearman’s
rank correlation coefficient when the
ranks are repeated is as follows
r
D
m m m m
n n
s = −
+
−
+
−
+






−
1
6
12 12
1
2
31 1
32 2
2
Σ
( ) ( )
...
( )
where m1
, m2
, ..., are the number
of repetitions of ranks and
m m
3
1 1
12
−
..., their corresponding
correction factors.
X has the value 35 both at the
4th and 5th rank. Hence both are
given the average rank i.e.,
4 5
2
4 5
+
=
th .
th
rank
X Y Rank of Rank of Deviation in D2
XR' YR'' Ranking
D=R'–R''
25 55 6 2 4 16
45 80 1 1 0 0
35 30 4.5 8 3.5 12.25
40 35 3 7 –4 16
15 40 8 5 3 9
19 42 7 4 3 9
35 36 4.5 6 –1.5 2.25
42 48 2 3 –1 1
Total ΣD = 65 5
.
The necessary correction thus is
m m
3 3
12
2 2
12
1
2
−
=
−
=
Using this equation
r
D
m m
n n
s = −
+
−






−
1
6
12
2
3
3
Σ
( )
...(5)
Substituting the values of these
expressions
rs = −
+
−
= −
= − =
1
6 65 5 0 5
8 8
1
396
504
1 0 786 0 214
3
( . . )
. .
Thus there is positive rank correlation
between X and Y. Both X and Y move
in the same direction. However, the
relationship cannot be described as
strong.
Activity
• Collect data on marks scored by
10 of your classmates in class IX
and X examinations. Calculate the
rank correlation coefficient
between them. If your data do not
have any repetition, repeat the
exercise by taking a data set
having repeated ranks. What are
the circumstances in which rank
correlation coefficient is preferred
to simple correlation coefficient? If
data are precisely measured will
you still prefer rank correlation
coefficient to simple correlation?
When can you be indifferent to the
choice? Discuss in class.
4. CONCLUSION
We have discussed some techniques
for studying the relationship between
2015-16

EXERCISES
1. The unit of correlation coefficient between height in feet and weight in
kgs is
(i) kg/feet
(ii) percentage
(iii) non-existent
2. The range of simple correlation coefficient is
(i) 0 to infinity
(ii) minus one to plus one
(iii) minus infinity to infinity
3. If rxy
is positive the relation between X and Y is of the type
(i) When Y increases X increases
(ii) When Y decreases X increases
(iii) When Y increases X does not change
two variables, particularly the linear
relationship. The scatter diagram gives
a visual presentation of the relationship
and is not confined to linear relations.
Karl Pearson’s coefficient of correlation
and Spearman’s rank correlation
measure linear relationship among
variables. When the variables cannot
Recap
• Correlation analysis studies the relation between two variables.
• Scatter diagrams give a visual presentation of the nature of
relationship between two variables.
• Karl Pearson’s coefficient of correlation r measures numerically only
linear relationship between two variables. r lies between –1 and 1.
• When the variables cannot be measured precisely Spearman’s rank
correlation can be used to measure the linear relationship
numerically.
• Repeated ranks need correction factors.
• Correlation does not mean causation. It only means
covariation.
be measured precisely, rank
correlation can be used. These
measures however do not imply
causation. The knowledge of
correlation gives us an idea of the
direction and intensity of change in a
variable when the correlated variable
changes.
2015-16

CORRELATION 105
4. If rxy
= 0 the variable X and Y are
(i) linearly related
(ii) not linearly related
(iii) independent
5. Of the following three measures which can measure any type of relationship
(i) Karl Pearson’s coefficient of correlation
(ii) Spearman’s rank correlation
(iii) Scatter diagram
6. If precisely measured data are available the simple correlation coefficient
is
(i) more accurate than rank correlation coefficient
(ii) less accurate than rank correlation coefficient
(iii) as accurate as the rank correlation coefficient
7. Why is r preferred to covariance as a measure of association?
8. Can r lie outside the –1 and 1 range depending on the type of data?
9. Does correlation imply causation?
10. When is rank correlation more precise than simple correlation coefficient?
11. Does zero correlation mean independence?
12. Can simple correlation coefficient measure any type of relationship?
13. Collect the price of five vegetables from your local market every day for a
week. Calculate their correlation coefficients. Interpret the result.
14. Measure the height of your classmates. Ask them the height of their
benchmate. Calculate the correlation coefficient of these two variables.
Interpret the result.
15. List some variables where accurate measurement is difficult.
16. Interpret the values of r as 1, –1 and 0.
17. Why does rank correlation coefficient differ from Pearsonian correlation
coefficient?
18. Calculate the correlation coefficient between the heights of fathers in inches
(X) and their sons (Y)
X 65 66 57 67 68 69 70 72
Y 67 56 65 68 72 72 69 71
(Ans. r = 0.603)
19. Calculate the correlation coefficient between X and Y and comment on
their relationship:
X –3 –2 –1 1 2 3
Y 9 4 1 1 4 9
(Ans. r = 0)
2015-16

Activity
• Use all the formulae discussed here to calculate r between
India’s national income and exports taking at least ten
observations.
20. Calculate the correlation coefficient between X and Y and comment on
their relationship
X 1 3 4 5 7 8
Y 2 6 8 10 14 16
(Ans. r = 1)
2015-16

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