\(\begin{array}{c|c}
Scores & 0 - 4 & 5 - 9 & 10 - 14\\
\hline Frequency & 2 & 1 & 2\end{array}\)

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

A.

5.6

B.

6.2

C.

6.6

D.

7.0

Correct answer is D

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