Epidemiology module of practical skills for mbbs student

Sub groups of the population: the denominator may be subgroups of population e.g. under-five, female, doctors, etc.

2. 
   Denominator related to total events: In some instances, the denominator may be related to total events instead of the total population, as in the case of infant mortality rate the denominator is total number of live births.
   

3. MEASURES OF CENTRAL TENDENCY

We need to workout averages for large number of values to make some sense. It gives the mental picture of the central value. There are several kinds of average, of which the commonly used are arithmetic mean, mode and median. Averages are measures of central value, therefore they locate the center or mid point of a distributions.

(a) Mean: To obtain the mean the individual observations are added together, and then divided by the number of observations.

(b) Mode: The mode is the most commonly occurring value in a distribution of data.

(c) Median: To obtain the median, the data is first arranged in a descending and ascending order the value of middle observation is located, which is called median.

EXERCISE