Question

Find out the mean of the following distribution:
Items
0-5
5-10
10–15
15-20
20-25
25-30
30-35
35-40
Frequency
2
5
7
13
21
16
8
3​

Answer 1

class interval frequency midpt Σfx

0-5 2 2.5 5

5-10 5 7.5 37.5

10-15 7 12.5 87.5

15-20 13 17.5 227.5

20-25 21 22.5 472.5

25-30 16 27.5 440

30-35 8 32.5 260

35-40 3 37.5 112.5

total n= 75 1642.5

=mean =Σfx/n

= 1642.5/75

= 21.5