Cumulative frequency series is that series in which the frequencies are continuously added corresponding to each class interval in the series. The frequencies that become cumulative frequencies. The cumulative frequency for the first class interval is the same as frequency itself.
But for the second class interval the cumulative frequency for the first class interval is the same as frequency itself. But for the second class interval the cumulative frequency would be the both the second as well as first class intervals, e.g.
| Marks |
Frequency |
Cumulative frequencies |
| 5 - 10 |
2 |
2 |
| 10 - 15 |
5 |
2 + 5 = 7 |
| 15 - 20 |
7 |
7 + 7 = 14 |
| 20 - 25 |
8 |
14 + 8 = 22 |
| 25 - 30 |
18 |
22 + 8 = 30 |
