Biostatistics.pptxhgjfhgfthfujkolikhgjhcghd

Definition
Meaning & Definition of Statistic:
• The word statistics usually conveys to a lay man an
impression about numerical facts.
• But to a scientific worker it means the
methodology of collection, compilation and
interpretation of numerical facts.
• The numerical facts, which are comes across in
health or biological sciences, such as pulse rate,
haemoglobin percentages level, number of births
and deaths taking place in a year etc.,
• The methodology of such collection and
meaningful interpretation of numerical facts is
known as “Statistics”.

Biostatistics:
• This branch deals with the methodologies of collection,
elucidation and interpretation of numerical facts
relation to the biological science. Medical Statistics is a
part of this broader science.
• It is the application of statistical techniques to scientific
research in health related fields, including medicine,
biology, and public health, nursing, and the
development of new tools to study these areas. The
different types of biostatistics and medical statistics,
health statistics and vital statistics.

Application of Biostatistics
• To identify the existing health problems of a community by
its size, nature and distribution of disease amongst the
various populations, so that the existing health facilities can
be utilized with maximum effects.
• To compare the health status of one community with the
other or the same community at two different periods. E.g.
compare of IMR, MMR, etc..
• To predict health trends (historical & forecasted to
determine prevention measures.
• To determine the success or failure of different health
programs and thereby fix suitable targets for its
achievements.
• to conform whether the statistical test is significant or not
between controlled & uncontrolled groups. E.g. the
significant difference is obtained by using deaths among
cigarette smokers and non-smoker groups.

Measure of Central Tendency
• Any type of data is considered as a single value and such a
single value expression of data is called central tendency.
• Central tendency may also be called central value.
• Measures of central tendency convey information
regarding the value of a set of data and is a synonym of
“average”.
• It is commonly used in our daily life like average income of
a family, average test result of lab technician students,
average height of under five children, average wt. of new
born babies, etc.
• Measures of central tendency are summary of statistics
used to indicate central location of a group of data values.
• There are three types of Central Tendency OR Average:
– Mean
– Median
– Mode

Mean
• Mean or Arithmetic mean is widely used in statistical
calculation.
• To obtain the mean, the individual observations are
first added together, and then divided by the number
of observations.
• The operation of adding together is called ‘summation’
and is denoted by the sign ∑ or S.
• The individual observation is denoted by the sign Xi
and the mean is denoted by sign X
• Mean (X) =
𝑠𝑢𝑚 𝑜𝑓 𝑎𝑙𝑙 𝑡ℎ𝑒 𝑜𝑏𝑠𝑒𝑟𝑣𝑎𝑡𝑖𝑜𝑛𝑠 𝑜𝑓 𝑡ℎ𝑒 𝑑𝑎𝑡𝑎
𝑁𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑜𝑏𝑠𝑒𝑟𝑣𝑎𝑡𝑖𝑜𝑛𝑠 𝑖𝑛 𝑡ℎ𝑒 𝑑𝑎𝑡𝑎
• 𝑿 = (∑Xi)/ n
• n is the number of observations in the data.

• E.g.: systolic blood pressure in mm Hg of ten
students are as follows:
115, 117, 121, 120, 118, 122, 123, 116,118, 120.
• Mean =
115+117+121+120+118+122+123+116+118+120
10
= 1190/10 = 119 mmHg

Median
• The median is an average of different kind,
which does not depend upon the total and
number of items.
• To obtain the median, the ungrouped data is
first arranged in an ascending or descending
order of magnitude, and then the value of the
middle observation is located, which is called
the median.

e.g.
• In a hospital ward the following are the
number of days of stay of patients.
13,42,8, 9, 7, 3, 6, 52, 8, 2, 11, 11, 10, 9.
• For the calculation of the median all the
numbers are first arranged in the order of
their magnitude.
2, 3, 6, 7, 8, 8, 9, 9, 10, 11, 11, 13, 42, 52
• As there are 14 patients, the average of the
period of stay corresponding to the 7th and 8th
patients is calculated as the median.
i.e. Median = (9+9)/2 = 9

Mode
• Another measure of central tendency, which is
less influenced by the value of the individual
observation, is the mode.
• This corresponds to that value of the
observation, which has highest frequency.
• In other words mode can be defined as the
most common value of the observation.
• It is calculated as
Mode = 3(median)-2(mean).

Measures of Dispersion or Variation
• The daily calorie requirement of a normal adult
doing sedentary work is laid down as 2400
calories. This clearly is not universally true.
• There must be individual variations. If we
examine the data of blood pressure or heights
or weights of a large group of individuals, we
will find the values vary from person to person.
• Even within the same subject, there may be
variation from time. The questions that arise
are:
– What is normal variation?
– And how to measure the variation?

• There are several measures of variation (or
dispersion) of which the following are widely
known:
– The Range
– The Mean or Average Deviation
– The Standard Deviation

The Range
• The range is far the simplest measure of
dispersion.
• It is defined as the difference between the
highest and lowest figures in a given sample.
• E.g. from the following record of diastolic blood
pressure of 10 individuals-
83, 75, 81, 79, 71, 90, 75, 95, 77, 94.
• it can be seen that the highest value was 95 and
the lowest 71.
• The range is expressed as 71 to 95 or by the
actual difference 24.

The Mean Deviation
• It is the average of the deviations from the
arithmetic mean. It is given by the formula:
M.D =
∑( 𝐗−𝐗 )
ᶯ
• E.g. The diastolic blood pressure of 10
individuals was as follows:
83, 75, 81, 79, 71, 95, 75, 77, 84, & 90.
Find the mean deviation.

Biostatistics.pptxhgjfhgfthfujkolikhgjhcghd

The Standard Deviation
• The standard deviation is the most frequently
used measure of deviation.
• In simple terms, it is defined as "Root -Means -
Square - Deviation.“
• It is denoted by the Greek letter sigma (Ϭ)or
by the initials S.D. The standard deviation is
calculated from the basic formula :
–S.D. =
∑ 𝐗−𝑿 𝟐
ᶯ
if the sample size >30.
–S.D. =
∑ 𝐗−𝑿 𝟐
ᶯ −1
if the sample size <30 .

• E.g. The diastolic blood pressure of
10 individuals was as follows : 83, 75,
81, 79, 71, 95, 75, 77, 84, 90.
• Calculate the standard deviation.
• Answer :

Health Research
Meaning :
• Research is careful investigation or inquiry,
especially through scientific methods, aimed
at searching new facts or verification of
established facts under various situations, in
any branch of knowledge.
• Scientific research is a systematic and
objective attempt to provide answers to
certain questions.

Definition
• The appropriate definition would be “an
honest, exhaustive, intelligent for the facts and
their implications with reference to a given
problem, which may lead to development of
theories, concepts, generalizations and
principles.

Objectives of health
• To find new generalization of health related matters with old
data.
• To bring light to the health related information trust.
• To discover an unexplored horizon of health knowledge or
extension of knowledge.
• To review old conclusions with new data.
• To attempt to reach more conclusions from the same set of data.
• To fine and resolve contradictions existing in the area of study.
• To analyze interrelationship between variables and to derive
causal explanation and thus enable to have a better
understanding of the world.
• To develop new tools, concepts and theories for better study of
unknown phenomenon.
• To find solutions to health problems.
• To make plans and thus contribute to national health
development.

Types of Research
• Research can be broadly of two types:
– Fundamental
– Applied
• Fundamental Research is a formal and systematic
process.
• Here the researcher’s aim is to develop a theory or
a model by identifying all the important variables
in a situation and discover broad generalization
and principles about the variables.
• It is utilizes a careful sample so that, conclusions
can be generalized beyond the immediate
situation.
• Fundamental research may not have concern with
its immediate application.

Applied Research
• Where the investigator applies the findings of the
basic or fundamental research to understand the
implications in real situations.
• This type of research tends to make generalizations
about the populations and uses certain statistical
techniques in selecting the sample for the study.
• Here the main purpose is not to develop theories but
to apply the theories to actual situations.
• E.g. when it is known that a disease is caused because
of deficiency of a particular nutrient in the food and if
a research is undertaken to supplement this particular
nutrient in the diseased persons, to understand the
outcome of this procedure on the disease in relation
to various other factors, the research is an applied
one.

Action Research:
• In health management, the research can be action
oriented when it is called as Action Research.
• In such research the main emphasis would be to
gain knowledge in undertaking different types of
actions to increase the efficiency of the services.
• In Action Research, researcher emphasizes a
problem which is immediate, urgent, and has local
application and focuses on the immediate
consequences and applications of a problem and
not on generalizations.

Operation Research
• Where the investigators is investigating a
particular set of actions to suggest improved
efficiency in terms of certain defined parameters
of outcome of such actions.
• Researcher focuses on finding out a best way of
carrying out an activity when there are more than
one option to attain a desired result when
desired result is clearly defined.
• It involves a combination of research approaches.
• Operation research emphasizes on taking
decisions.

Experimental Research & Non-experimental Research
• In experimental research, which may be either
laboratory experiment or field experiment,
independent variables can be manipulated where as
in Non-experimental research independent variables
cannot be manipulated.
• In Laboratory research, experimenter can control
the variables as needed and the results can be
interpreted precisely under these conditions.
• Field Experiments are carried out in realistic
situations where independent variables cannot be
manipulated. Common methods of field
experiments are descriptive studies to describe
certain phenomenon under realistic situation.

Methods of Research
• There are main 2 types of study methods are in
health research. They are:
1. Observational studies &
2. Experimental studies/ Interventional studies.
1. Observational studies:
a. Descriptive studies
b. Analytical studies
i. Ecological or correlational or longitudinal ( with
populations as a unit)
ii. Cross-sectional or prevalence ( with individuals as a unit of
study)
iii. Case-control or Case-reference (with individuals as a unit of
study)
iv. Cohort or Follow-up ( with individuals as a unit of study)

2. Experimental studies/ Interventional
studies.
a. Randomized controlled trials or Clinical trials (
with patients as unit of study)
b. Field trials or Community intervention studies (
with healthy people as unit of study)
c. Community trials ( with communities as a unit
of study)

Descriptive Studies
• These studies are concerned with observing the
distribution of disease or health related
characteristics in human populations and
identifying the characteristics with which the
disease in question seems to be associated. Such
studies basically ask the question.
– When is the disease occurring?
» time distribution
– Where is it occurring?
» Place distribution
– Who is getting the disease?
» Person distribution

• The various procedures involved in
descriptive studies may be outlined as below:
Defining the population to be studied
Defining the disease under study
Describing the disease by
a. Time
b. Place
c. Person
Measurement of disease
Comparing with known indices
Formulation of an aetiological hypothesis

Cross-sectional studies
• Cross-sectional study is the simplest form of an
observational study.
• It is based on a single examination of a cross-
section of population at one point in time - the
results of which can be projected on the whole
population provided the sampling has been
done correctly.
• Cross-sectional study is also known as
"prevalence study".

• Cross-sectional studies are more useful for chronic
than short-lived diseases.
• E.g. in a study of hypertension, we can also collect
data during the survey about age, sex, physical
exercise, body weight, salt intake and other
variables of interest.
• Then we can determine how prevention of
hypertension is related to certain variables
simultaneously measured.
• Such a study tells us about the distribution of a
disease in population rather than its aetiology.
• This type of studies give possible ways of preventing
disease.

Longitudinal studies
• Longitudinal studies are useful
(i) to study the natural history of disease and its future
outcome
(ii) for identifying risk factors of disease, and
(iii) for finding out incidence rate or rate of occurrence
of new cases of disease in the community
• Longitudinal studies provide valuable information
which the cross-sectional studies may not provide,
but longitudinal studies are difficult to organize and
more time-consuming than cross-sectional studies.

• Measurement can also be extended to health
states and events.
• For example, the study of blood pressure levels
in a population will reveal the normal values,
rather than abnormal ones related to disease.

Analytical Studies
• In contrast to descriptive studies that look entire
populations, in analytical studies, the subject of
interest is the individual within the population.
• The object is not to formulate, but to test
hypothesis.
• Analytical studies comprise two distinct types of
observational studies:
a. Case control study
b. Cohort study

Case Control Study
• Case control studies often called “retrospective
studies”.
• The case control method has three distinct
feathers:
Both exposure and outcome (disease) have occurred
before the start of the study.
The study proceeds backwards from the effects to
cause and
It uses a control or comparison group.

• A case control study involves two populations-cases
& controls.
• In case control studies, the unit is the individual
rather than the group.
• The focus is on a disease or some other health
problem that has already developed.
Steps of case control study:
i. Selection of cases and control
ii. Matching
iii. Measurement of exposure, and
iv. Analysis and interpretation.

Cohort Study
• Cohort study is another type of analytical
(observational) study which is usually
undertaken to obtain additional evidence to
refute or support the existence of an
association between suspected causes and
disease.
• Cohort study is known by a variety of names;
prospective study, longitudinal study, incidence
study, and forward-looking study. The most
widely used term, however is “cohort study”.

The distinguishing features of cohort
studies are:
a. The cohorts are identified prior to the
appearance of the disease under
investigation.
b. The study groups, so defined, are observed
over a period of time to determine the
frequency of disease among them
c. The study proceeds forward from cause to
effect.

Types of cohort studies
I. Prospective cohort studies: A prospective study (or
“current study” cohort study) is one in which the
outcome (e.g., disease) has not yet occurred at the
time the investigation begins. Most prospective
studies begin in the present and continue into future.
II. Retrospective cohort studies: A retrospective cohort
study (or "historical" cohort study) is one in which the
outcomes have all occurred before the start of the
investigation. The investigator goes back in time,
sometimes 10 to 30 years, to select his study groups
from existing records of past employment, medical or
other records and traces them forward through time,
from a past date fixed on the records, usually up to
the present.

Elements of cohort study
1. Selection of study subjects
2. Obtaining data on exposure
3. Selection of comparison groups
4. Follow-up, and
5. Analysis

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