Class interval: | 0-8 | 8-16 | 16-24 | 24-32 | 32-40 |
Frequency: | 6 | 7 | 10 | 8 | 9 |
Let the assumed mean (A) = 20
Class interval | Mid – value (xi) | di = xi - 20 | ui = | Frequency (fi) | fiui |
0 – 8 | 4 | -16 | -2 | 6 | -12 |
8 – 16 | 12 | -8 | -1 | 7 | -17 |
16 – 24 | 20 | 0 | 0 | 10 | 0 |
24 – 32 | 28 | 8 | 1 | 8 | 8 |
32 - 40 | 36 | 16 | 2 | 9 | 18 |
N = 40 | ∑fiui = 7 |
We have, A = 20
h = 8
Mean = A + h *
= 20 + 8 *
= 20 + 1.4 = 21.4