Here, preparing a table to calculate the mean, we get.
Marks obtained (X) | No of students(F) | Mid value(M) | FM |
5 - 15 | 3 | 10 | 30 |
15 - 25 | 5 | 20 | 100 |
25 - 35 | 9 | 30 | 270 |
35 - 45 | 3 | 40 | 120 |
45 - 55 | 2 | 50 | 100 |
N = 22 | Σfm = 620 |
Now, by formula
mean (X) = Σfm/N
= 620/22
= 28.18
Therefore, the mean is 28.18.