Maths Dictionary · SS 2
Ogive
Simple meaning
The S-shaped graph of cumulative frequency. You read the median and quartiles from it.
Example
With 40 students, the median is read at the 20th value.
See it
From the Cumulative Frequency lesson. Try moving things around.
Cumulative freq.20
About 20 of the 40 scored 30.5 or less.
Median
≈ 30.5
at n/2 = 20
Q₁
≈ 19.2
at n/4 = 10
Q₃
≈ 38.7
at 3n/4 = 30
IQR
≈ 19.4
Q₃ − Q₁
| Marks | f | Upper bound. | Cum. freq. |
|---|---|---|---|
| 1–10 | 4 | 10.5 | 4 |
| 11–20 | 7 | 20.5 | 4 + 7 = 11 |
| 21–30 | 9 | 30.5 | 11 + 9 = 20 |
| 31–40 | 12 | 40.5 | 20 + 12 = 32 |
| 41–50 | 8 | 50.5 | 32 + 8 = 40 |