WAEC - Mathematics (2015 - No. 25)

Score	0 - 4	5 - 9	10 - 14
Frequency	2	1	2

The table shows the distribution of the scores of some students in a test. Calculate the mean scores.

5.6

6.2

6.6

7.0

To calculate the mean of grouped data,

- First step to determine the midpoint (x) of each interval or class.

0 - 4 ►2

5 - 9 ► 7

10 - 14 ►12

These midpoints must then be multiplied by the frequencies of the corresponding classes:

2 X 2 = 4

1 X 7 = 7

2 X 12 = 24

Mean = ( 24 + 7 + 4) ÷ ( 2 + 1 + 2 )

: Mean = 7