Measures of Dispersion for Grouped Data
Cumulative frequency
A running total of frequencies, used to plot an ogive.
| English | Cumulative frequency |
|---|---|
| Bahasa Melayu | Kekerapan longgokan |
| 中文 | 累积频数 |
How it is used
For classes with frequencies 3, 7, 12, 6, 2, the cumulative frequencies are 3, 10, 22, 28 and 30. Each is the running total up to that class, and the final value 30 equals the total number of data, Σf.
Where it shows up in SPM
In grouped-data statistics, Form 5. In Paper 2 you first build a cumulative frequency column from the frequency table, then plot it against upper boundaries to draw the ogive.
The last cumulative frequency should always equal Σf, a quick check that your addition is correct.
Don't confuse it with
Open the chapter: Measures of Dispersion for Grouped Data →
Frequently asked questions
How do I build a cumulative frequency column?
Start with the first frequency, then add each class frequency to the total so far. For 3, 7, 12, 6, 2 you get 3, then 3+7=10, then 10+12=22, then 22+6=28, then 28+2=30, matching the total of 30.
Against which value do I plot cumulative frequency?
Plot each cumulative frequency against the upper boundary of its class, not the midpoint. That is because the running total includes everyone up to the top of the class, so the point belongs at the class's upper edge.