Introduction to Biostatistics

Prof.Dr.Sahar Khashab

Community Medicine Department

Learning Objectives:

After completing this session, students will be able to:

1. recognize the uses of biostatistics

in medicine.

2. classify variables.

Definition

• Statistics is the scientific field that

deals with collection, classification,

presentation, description, analysis &

interpretation of data.

Distribution of country (A) population by Age and Sex

1986 Census

Total Female Male

Age % No. % No. % No.

15.3

13.1

11.6

10.5

8.8

7.7

6.3

6.1

4.4

4.0

3.5

2.6

2.3

1.4

1.1

0.8

0.6

7362181

6341086

5577920

5063632

4247541

3697508

3045324

2925306

2127952

1915240

1695676

1252294

1131213

682491

530116

385917

272841

7.7

6.5

5.6

5.0

4.3

4.0

3.2

3.1

2.3

2.0

1.9

1.3

1.2

0.7

0.5

0.4

0.3

3608333

3070428

2647282

2370734

2024869

1909065

1530714

1433555

1073015

942756

899538

579157

577203

330227

226808

190880

120400

7.6

6.6

6.0

5.5

4.5

3.7

3.1

3.0

2.1

2.0

1.6

1.3

1.1

0.7

0.6

0.4

0.3

3753848

327658

293638

2692898

2222672

1788443

1514610

1491751

1054937

972484

796138

673137

554010

352264

293308

195037

152441

Less than 5

5-

10-

15-

20-

25-

30-

35-

40-

45-

50-

55-

60-

65-

70-

75+

Missed

100 48254238 50 23544964 50 24709274 Total

Population Pyramid of Egypt 2000

0

10

20

30

40

50

60

70

80

90

1st Qtr 2nd Qtr 3rd Qtr 4th Qtr

East

West

North

Frequency Blood group

4

8

5

3

A

B

AB

O

20 Total

0

1

2

3

4

5

6

7

8

9

A B AB O

Blood group

Fre

qu

en

cy

1- Descriptive statistics:

which is concerned with the summary

measures of data for a sample of a

population.

Example.

Analytic statistics: -2

Concerned with the use of data from a

sample of population to make inferences

about the population.

Examples

Smoking Lung cancer Total

YES + NO -

YES +

Exposed

20 a

+ +

180 b

+ -

200 a+b

NO -

Not exposed

2 c

+ -

198 d

- -

200 c+d

Total ----------- ------------ ------------

Find out RR and AR for above data

Vital statistics: -3

It is the ongoing collection by government

agencies of data relating to events such as

births, deaths, marriage, divorces, health

and disease related conditions reportable

by local health authorities.

Examples

Biostatistics

Application of statistical procedures in

the field of biological sciences &

medicine

Uses in Medicine:

• Biostatistics is necessary for both clinical and preventive medicine.

• Physicians should have the basic knowledge for evaluation and criticism of researches published in medical journals.

• Statistics is helpful to assess diagnostic testing and to assess the effects of new drugs and treatment modalities.

• Epidemiologists need to know how to calculate rates, to compare between groups and to decide how likely the differences in comparison groups could be due to chance.

Total number of life births in a certain

year and locality

Estimated midyear population ( same

year and locality)

=… Live Births/ 1000 population in a year

Crude Birth Rate

X 1000

Data

• are the basic building blocks of statistics

and refer to the individual values

measured or observed. Data can be

derived from a total population or a

sample.

Methods of collection of data

By conducting survey:

• The investigator collects the data from the

population in the field of the study using a

designed questionnaire.

There are two types of surveys

Comprehensive surveys:

• When the data are collected from every member in the population (the total population present in the field of the study) but this type requires a great deal of time, great effort and money and only used in census.

Sample survey:

• Where the collection of data is conducted on a representative sample could be generalized over the total population.

• This method is commonly used for collection of data since it requires less effort, time and money.

Data collected from records:

Data are already present.

Sources of these data:

• Population census.

• Hospital records.

• School health records.

• Vital statistics; these are published yearly and contain data about births, deaths and morbidity.

• Text-books and scientific journals.

:Types of data

Data are classified into:

Constant data:

These are observations which do not vary from one person to another such as number of eyes, fingers, ears… etc

Variables:

These are observations, which vary from one person to another or from one group of members to others and are subdivided into the following:

:Quantitative variables

These may be continuous or discrete.

• a- Continuos quantitative variable:

Which are obtained by measurement and

its value could be integer or fractionated

value.

Examples:

Weight, height, hemoglobin, age, income,

volume of urine.

Discret or discontinus quantitative -B

:variables

• Which are obtained by enumeration and

its value is always integer value.

Examples:

Pulse, family size, number of live births,

number of abortions.

Qualitative variables

Which are expressed in quality and cannot

be enumerated or measured but can be

categorized only.

They can be ordinal or nominal

a- Ordinal qualitative:

Can be put in order:

Examples

Degree of success

• excellent

• very good

• good

• fair

Degree of a disease:

• mild

• moderate

• severe

b- Nominal qualitative:

Can not be put in order and is further subdivided into:

• Dichotomous Examples

sex

yes/no variables

• Multichotomous Examples

marital status

blood groups