Find the mean of the following frequency distribution:
Class | 1 - 3 | 3 - 5 | 5 - 7 | 7 - 9 |
Frequency | 9 | 22 | 27 | 18 |
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 | 9 | 18 |
3 - 5 | 4 | 22 | 88 |
5 - 7 | 6 | 27 | 162 |
7 - 9 | 8 | 18 | 144 |
TOTAL | 76 | 412 |
We have got
Σfi = 76 & Σfixi = 412
∵ mean is given by
⇒
⇒
Thus, mean is 5.421