Elementary Statistics (1+1)

4.2.2.5 ‘Inclusive’ Method

Under the ‘inclusive’ method of classification, the upper limit of one class is included in that class itself. The following example, illustrates the method :

Income (Rs.)	No. of Persons
1000-1099 1100-1199 1200-1299 1300-1399 1400-1499 1500-1599	50 100 200 150 40 10
TOTAL	550

In the class 1000-1099 we include persons whose income is between Rs.1000 and Rs.1099. If the income of a person is exactly Rs.1100 he is included in the next class. The above example makes it clear that there is no confusion here of the type we find under the ‘exclusive’ method. We may have classes like 1000-1099.5 or 1000-1099.99, and so on.

To decide whether to use the inclusive or the exclusive method it is important to determine whether the variable under observation is a continuous or discrete one. In case of continuous variables the upper limit exclusive method must be used. For example, the variable height being inherently a continuous one should be stated as 60” and under 62”,62" and under 64”, and so on. The inclusive method should, in general, be used in case of discrete variables. Thus, in classifying factories according to number of workers, the limits should be stated as, for example, 100-199 employees, 200-299 employees and not 100-200, 200-300, etc.