Statistics

What is Data?

Data are facts or figures from which conclusion may be drawn. Or
Data is a collection of facts, such as values or measurements.
It can be numbers, words, measurements, observations or even just
descriptions of things.
Data are the raw material of statistics. Statistical analysis cannot proceed until the data
interest in an investigation are assembled and organized in a useful manner. We shall
refer to the data collected for a particular study as a Data Set.
Each Data set contains observations on the variables of interest for the elements in the
data set.
Elements: A data set represents a collection of elements (Country), and for each
element information on one or more characteristic of interest (Birth Rate) is included in
the data set e.g.,
Country Birth Rate
A 19.8
B 20.7
C 25.8

Prepared By: Sayed Burhan Atal

Conti.
Qualitative vs Quantitative
Data can be qualitative or quantitative.
Qualitative data is descriptive information (it describes something)
Quantitative data, is numerical information (numbers).
And Quantitative data can also be Discrete or Continuous:
Discrete data can only take certain values (like whole numbers)
Continuous data can take any value (within a range)
Put simply: Discrete data is counted, Continuous data is measured

Types of Data

Data

Quantitative Qualitative
(Numeric) (Non - Numeric)

Variable
A quantity that, varies from an individual to
individual. Or A characteristic that can
take on different possible outcomes is
called a Variable.
Variable

Qualitative (Non - Numeric): If the
Quantitative (Numeric) : If the outcome outcomes refer to non-numerical qualities
Are expressed numerically, the variable or attributes, the variable is said to be
is said to be quantitative. qualitative.

Population etc.

Population: The totality of elements (persons, farms,
firms) under study is called the population.
Census: A survey that includes every element in the
population is called a census.
Sample and Sample Survey: A sample is a portion of
the population. A survey that includes only a
portion of the population is called a sample survey.

OBSERVATIONS AND VARIABLES

Observations:
In statistics, an observation often means any sort of
numerical recording of information, whether it is a physical
measurement such as height or weight; a classification such as
heads or tails, or an answer to a question such as yes or no.
Variable:
A characteristic that varies with an individual or an
object, is called a variable.
For example, age is a variable as it varies from person to
person. A variable can assume a number of values.

Statistics deals with numbers
 Need to know nature of numbers collected
1. Continuous variables: type of numbers
associated with measuring or weighing; any
value in a continuous interval of
measurement.
 Examples:

– Weight of students, height of plants, time to flowering

1. Discrete variables: type of numbers that are
counted or categorical
 Examples:

– Numbers of boys, girls, insects, plants

Can you figure out…
 Which type of numbers (discrete or
continuous?)
– Numbers of persons preferring Brand X in 5
different towns
– The weights of high school seniors
– The lengths of oak leaves
– The number of seeds germinating
– 35 tall and 12 dwarf pea plants
– Answers: all are discrete except the 2nd and 3rd
examples are continuous.

EXAMPLES OF DATA

Data are collected in many aspects of everyday life.
• Statements given to a police officer or physician or
psychologist during an interview are data.
• The correct and incorrect answers given by a student on a final
examination.
• Almost any athletic event produces data.
• The time required by a runner to complete a marathon,
• The number of errors committed by a baseball team in nine innings
of play, and
• So on.

QUANTITATIVE & QUALITATIVE VARIABLES

Variables may be classified into quantitative and qualitative according
to the form of the characteristic of interest.
• A variable is called a quantitative variable when a characteristic can be
expressed numerically such as age, weight, income or number of children.
On the other hand, if the characteristic is non-numerical such as
education, sex, eye-colour, quality, intelligence, poverty, satisfaction, etc.
• where the variable is referred to as a qualitative variable. A qualitative
characteristic is also called an attribute.
An individual or an object with such a characteristic can be counted or
enumerated after having been assigned to one of the several mutually exclusive
classes or categories.

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