Question :
| Number of plants | 0 – 2 | 2 – 4 | 4 – 6 | 6 – 8 | 8 – 10 | 10 – 12 | 12 – 14 |
| No. of houses | 1 | 2 | 1 | 5 | 6 | 2 | 3 |
Which method do you use for finding the mean and why ?
Solution :
| Number of Plants | Number of houses \(f_i\) | Mid-value x | fx |
| 0 – 2 | 1 | 1 | 1 |
| 2 – 4 | 2 | 3 | 6 |
| 4 – 6 | 1 | 5 | 5 |
| 6 – 8 | 5 | 7 | 35 |
| 8 – 10 | 6 | 9 | 54 |
| 10 – 12 | 2 | 11 | 22 |
| 12 – 14 | 3 | 13 | 39 |
| \(\sum f_i\) = 20 | \(\sum f_ix_i\) = 162 |
Mean = \(\sum f_ix_i\over \sum f_i\) = \(162\over 20\) = 8.1
Here, we have used direct method because numerical values of \(x_i\) and \(f_i\) are small.
