Class-interval | 0−10 | 10−20 | 20−30 | 30−40 | 40−50 | 50−60 |
Frequency | 7 | 14 | 28 | 26 | 16 | 9 |
class interval | frequency (f) | mean value (x) | fx |
0 - 10 | 7 | 5 | 35 |
10 - 20 | 14 | 15 | 210 |
20 - 30 | 28 | 25 | 700 |
30 - 40 | 26 | 35 | 910 |
40 - 50 | 19 | 45 | 720 |
50 - 60 | 9 | 55 | 495 |
Sum | 100 | 3070 |