Biostatistics

Vital statistics:

probably the major source of information about the health of population is its vital statistics. By vital statistics we mean the data collected from ongoing recording, or registration of all "vital events”, deaths, marriages, adoptions, and fetal deaths, divorces, legal separations and annulments. We will discuss only those aspects of registration with which physician are much concerned certification of

deaths, births and fetal deaths.

Epidemiology:

Epidemiology is the study of the distribution and Determinant of diseases and injuries in

human population .

Statistics:

The term statistics is concerned with scientific methods for collecting, organizing, presenting and analysis data, as well as drawing valid conclusions and making reasonable decisions on the basis of such analysis.

Bio Statistics:

Is the branch of statistics, which deal with collecting, presenting, summarizing, analyzing

and interpreting sets of data in health field .

Scale of measurements

Nominal scale

Ordinal or raking scale

Interval scale

Ratio scale

A variable:

It is a value of characteristics that changes from one subject to another, from thing to thing

variables can be divided to:

1.Qualitative variable

2.Quantitative variable. It is divided to:

A. Continuous variable

B. Discrete variable

Collection of data:

1.Regular or routine system:Consist of registration procedure for collecting data as

the become a variable .

2.AD HOC System:A survey to collect information that is not available on a regular basis. It is done for local administrative or research purpose.

Data Presentation

(a )Presentation of qualitative data:

1.Tabulation form

2.Graphical form

The basic rule for displaying qualitative data is to classify them into categories and then count the number of observations in each category of the variable and present the number and percentage in a table

Sex Frequency

Male 30

Female 20

Other 50

1 -Tabulation form:

Cross tabulation:

A Frequency table involving at least two variable that have been cross classified.

Example

Test ResultNo DiseaseDisease Total

Positive 10 80 90

Negative 190 20 210

Total 200 100 300

1.Graphical form:

1.Bar chart:

Is used with categories data, with nominal data

2 -Pie chart:

Sectors of a circle with areas proportional to class frequencies, used to present data in nominal classes

Example:Fig (1) the number of

students according to

the sex male

female

)B (Presentation of quantitative data:

1.Tabulation form

2.Graphic form

(1 )Tabulation form:

Example (1):Serum albumin value in g/ liter of blood of 50 women seen in survey are as follow:

42 , 41 , 42 , 44 , 44 , 36 , 38 , 41 , 42 , 44 , 42 , 39 , 49 , 40

,45 , 32 , 34 , 43 , 37 ,39 , 41 , 39 , 48 , 42 , 43 , 33 , 43

,35 , 32 , 34 , 39 , 35 , 43 , 44 , 47 , 40 , 39 , 42 , 41 , 46

,37 , 49 , 41 , 39 , 43 , 42 , 47 , 48 , 51 , 52.

Serum

Albumin (g/liter)

Number of observations

30 -3

34 -7

38 -14

42 -17

46 -7

50-53 2Total 50

2 -Graphic form:

1 -Histogram

2 -Frequency polygon )line chart(

3 -Frequency curve

4 -Cumulative frequency polygon )ogive(

Measure of central tenderly and location

Arithmetic's mean:

The sum of all values of a set of observations divided by the number of observations.

The median:

When a set of observation is the value that divides a distribution into two equal halves.

The mode:

The most frequently occurring in series of observations

Example:

For the following data 10 , 8 , 7 , 2 , 8 , 7 find the mean median and mode.

Solution:

The mean:

x =∑x

n =10 + 8 + 7 + 2 + 8 + 7= 7

6

The median:Array all the observations in a sending order

2,7,7,8,8,10

X = 8+7 / 2 = 7.5

The mode:

There are two modes:X=7 & 8

if the mean, the mode and the median are equal the distribution of observation is symmetric

If the mean larger than the median, the distribution is skewed to the right.

If the mean is smaller than the median , the distribution skewed to the left.