Find the mean, using direct method:
Class | 0 - 10 | 10 - 20 | 20 - 30 | 30 - 40 | 40 - 50 | 50 - 60 |
Frequency | 7 | 5 | 6 | 12 | 8 | 2 |
For equal class intervals, we will solve by finding mid points of these classes using direct method.
CLASS | MID - POINT(xi) | FREQUENCY(fi) | fixi |
0 - 10 | 5 | 7 | 35 |
10 - 20 | 15 | 5 | 75 |
20 - 30 | 25 | 6 | 150 |
30 - 40 | 35 | 12 | 420 |
40 - 50 | 45 | 8 | 360 |
50 - 60 | 55 | 2 | 110 |
TOTAL | 40 | 1150 |
We have got
Σfi = 40 & Σfixi = 1150
∵ mean is given by
⇒ 
⇒ 
Thus, mean is 28.75
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