How do you calculate the cumulative frequency for each class interval?

To calculate cumulative frequency, add the frequency of each class interval to the sum of all previous frequencies.

Cumulative frequency is a way to keep a running total of frequencies through the class intervals in a data set. To start, you need a frequency table that lists each class interval and its corresponding frequency. The first cumulative frequency is simply the frequency of the first class interval.

For the next class interval, you add its frequency to the cumulative frequency of the previous class interval. This process continues for each subsequent class interval. Essentially, you are adding each new frequency to the total of all the frequencies that came before it.

For example, if you have a frequency table with class intervals and their frequencies as follows:

- 0-10: 3
- 10-20: 5
- 20-30: 7
- 30-40: 4

The cumulative frequency for the first interval (0-10) is 3. For the second interval (10-20), you add 5 to the previous cumulative frequency of 3, giving you 8. For the third interval (20-30), you add 7 to the previous cumulative frequency of 8, resulting in 15. Finally, for the fourth interval (30-40), you add 4 to the previous cumulative frequency of 15, giving you 19.

So, the cumulative frequencies are:

- 0-10: 3
- 10-20: 8
- 20-30: 15
- 30-40: 19

This method helps you to see how the frequencies accumulate over the range of data, making it easier to analyse trends and patterns.