How is histogram constructed when class-intervals are unequal?
For constructing histogram of unequal class-intervals, first we note a class of the smallest intervals. Other classes are noted in the increasing order of their intervals. If the size of one class-interval is twice the smallest size in the series, frequency of that class is divided by two. Suppose the class with the smallest interval is 5 – 10 and the class with the largest interval is 10 – 20, the frequency of which is 12. Here the class interval of the bigger class is 10 which is twice as much as the size of the class-interval of the smallest class i.e. 5. The bigger class interval is divided into two parts 10 – 15 and 15 – 20 and accordingly the frequency of the bigger class, 12 would be divided by 2 i.e. 12+ 6. In this way there will be following adjustment.
|
Class-interval |
Frequency |
|
10 – 15 |
6 |
|
15 – 20 |
6 |
