Compute the mean of the following data:
Class | 1 - 3 | 3 - 5 | 5 - 7 | 7 - 9 |
Frequency | 12 | 22 | 27 | 19 |
For equal class intervals, we will solve by finding mid points of these classes using direct method.
CLASS | MID - POINT(xi) | FREQUENCY(fi) | fixi |
1 - 3 | 2 | 12 | 24 |
3 - 5 | 4 | 22 | 88 |
5 - 7 | 6 | 27 | 162 |
7 - 9 | 8 | 19 | 152 |
TOTAL | 80 | 426 |
We have got
Σfi = 20 & Σfixi = 426
∵ mean is given by
⇒ 
⇒ 
Thus, mean is 5.325
3