Biostatistics

Dr.G.PRIYA
ASSISTANT PROFESSOR
DEPARTMENT OF BIOTECHNOLOGY
SRM INSTITUTUTE OF SCIENCE AND TECHNOLOGY
RAMAPURAM, CHENNAI – 600 089.

Bio-Statistics in Various areas
Health Statistics
Medical Statistics
Vital Statistics

• In Public Health or Community Health, it is called Health
Statistics.
• In Medicine, it is called Medical Statistics. In this we study the
defect, injury, disease, efficacy of drug, Serum and Line of
treatment, etc.,
• In population related study it is called Vital Statistics. e.g.
study of vital events like births, marriages and deaths.

a.
b.
c.
d.
• Application and uses of Biostatistics as a science..
in Physiology,
to define what is normal/healthy in a population
to find limits of normality
to find difference between means and proportions of
normal at two places or in different periods.
to find the correlation between two variables X and Y such
as in height or weight..
for eg. Weight increases or decreases proportionately with
height and if so by how much has to be found.

• In Pharmacology,
a. To find action of drug
b. To compare action of two different drugs
c. To find relative potency of a new drug with respect to a
standard drug.
• In Medicine,
a. To compare efficacy of particular drug, operation or line of
treatment.
b. To find association between two attributes eg. Oral cancer and
smoking
c. To identify signs and symptoms of disease/ syndrome.

Common statistical terms
• Variable:- Acharacteristic that takes on different values in
different persons, places/ things.
• Constant:- Quantities that donot vary such as π = 3.141
e = 2.718
these donot require statistical study.
In Biostatistics, mean, standard deviation, standard error,
correlation coefficient and proportion of a particular
population are considered constant.
• Observation:- An event and its measurment.
for eg.. BP and its measurment..

• Observational unit:- the “sources” that gives observation for
eg. Object, person etc.
in medical statistics:- terms like individuals, subjects etc are
used more often.
• Data :- Aset of values recorded on one or more observational
units.
• Population:- It is an entire group of people or study elements-
persons, things or measurments for which we have an intrest
at particular time.
• Sampling unit:- Each member of a population.
• Sample:- It may be defined as a part of a population.

• Parameter:- It is summary value or constant of a variable, that
describes the sample such as its mean,
standard deviation
standard error
correlation coefficient etc..
• Parametric tests:- It is one in which population constants
such as described above are used :- mean,
variances etc..
data tend to follow one assumed or established distribution
such as normal, binomial, poisson etc..
• Non- parametric tests:- Tests such as CHI- SQUARE test, in
which no constant of population is used.
Data donot follow any specific distribution and no assumptions
are made in non- parametric tests.eg ..good, better and best..

American Heritage Dictionary® defines statistics as: "The
mathematics of the collection, organization, and interpretation of
numerical data, especially the analysis of population
characteristics by inference from sampling.”
The Merriam-Webster’s Collegiate Dictionary® definition is:
"Abranch of mathematics dealing with the collection, analysis,
interpretation, and presentation of masses of numerical data."
DEFINITION

Statistics is defined as the
Collection, Presentation,
Analysis and Interpretation
of numerical data.”

In the line of the definition of Croxton and Cowden, a
comprehensive definition of Statistics can be:
“Statistics defined as the science of
Collection,
Organisation,
presentation,
analysis and
interpretation of numerical data.”

• STATISTIC/ DATUM:- measured/ counted fact or piece of
information
such as height of person,
birth weight of baby…
• STATISTICS/ DATA:- plural of the same
such as height of 2 persons,
birth weight of 5 babies
plaque score of 3 persons…
• BIOSTATISTICS:- term used when tools of statistics are
applied to the data that is derived from biological sciences
such as medicine.

Types of Data
Qualitative Data Quantitative Data
Nominal Ordinal
Discrete Continuous
Interval Ratio

COLLECTION
OF DATA
Data can be collected through
Primary sources:- here data is obtained by the investigator
himself. This is first hand information.
Secondary sources:- The data already recorded is utilized to
serve the purpose of the objective of study eg. records of OPD
of dental clinics.

• Main sources for collection of medical statistics:-
1. Experiments
2. Surveys
3. Records.
• Experiments and surveys are applied to generate data needed
for specific purposes.
• While Records provide ready- made data for routine and
continuous information.

Methods of collection of data
• Method of direct observation:- clinical signs and symptoms
and prognosis are collected by direct observation.
• Method of house to house visit:- vital statistics and morbidity
statistics are usually collected by visiting house to house.
• Method of mailed questionnaire:- this method is followed in
community where literacy status of people is very high.
Prepaid postage stamp is to be attached with questionnaire.

Presentation of data
• to sort and classify data into groups or classification.
• Objective :- to make data simple,
concise,
meaningful,
intresting,
helpful for further analysis.
• 2 main methods are
i. Tabulations
ii. Charts and diagrams

• Tabulation :-
• Devices for presenting data simply from masses of statistical
data.
• Atable can be simple or complex, depending upon the number
or measurment of a single set or multiple set of items.
• 3 types:
a. Master table:- contains all the data obtained from a survey.
b. Simple table:- oneway table which supply answers to
questions about one characteristics only.
c. Frequency distribution table:- data is first split up into
convenient groups and the number of items which occur in
each group is shown in adjacent columns.

Table
1
states population 1st march 2011
Andhra pradesh 8,46,65,533
Madhya pradesh 7,25,97,565
Uttar pradesh 19,95,81,477
Karnataka 7,14,83,435
Rajasthan 18,23,45,998
kerela 6,43,35,772

Frequency distribution table
• The following figures are the ages of patients admitted to a
hospital with poliomyelitis..
8, 24, 18, 5, 6, 12, 14, 3, 23, 9, 18, 16, 1, 2, 3, 5, 11, 13, 15, 9,
11, 11, 7, 106, 9, 5, 16, 20, 4, 3, 3, 3, 10, 3, 2, 1, 6, 9, 3, 7, 14,
8, 1, 4, 6, 4, 15, 22, 2, 1, 4, 6, 4, 15, 22, 2, 1, 4, 7, 1, 12, 3, 23,
4, 19, 6, 2, 2, 4, 14, 2, 2, 21, 3, 2, 1, 7, 19.
Age Number of patients
0-4 35
5-9 18
10-14 11
15-19 8
20-24 6

Charts and diagrams
1. Histogram
2. Frequency polygon
3. Frequency curve
4. Line chart or graph
5.Cumulative frequency
diagram
6. Scatter diagram
Quantitative
data
1.Bar diagram
2.Pie or sector
diagram
3.Pictogram
4.Map diagram
Qualitative
data

Cumulative
frequency
diagram or
Ogive

Scatter or dot or correlation
diagrams

Biostatistics

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