# 7.1a Mean

7.1a Mean
1. The mean of the data is an average value obtained by using the formula:
Mean= Total data values Number of data

(A) Ungrouped Data

Example 1
(a) Find the mean for the set of data 2, 4, 7, 10, 13, 16 and 18.

(b) A value of xis added into the above set of data, the mean for  this new data is 9.5. Determine the value of x.

Solution:
(a)
$\begin{array}{l}\overline{x}=\frac{2+4+7+10+13+16+18}{7}\\ \overline{x}=\frac{70}{7}=10\end{array}$

(b)

(B) Grouped Data (Without Class Interval)

Example 2
The frequency table shows the marks obtained by 40 students in a Biology test.

Find the mean marks.

Solution:

(C) Grouped Data (With Class Interval)

Example 3
The grouped frequency distribution was obtained from 100 students regarding the scores in their test shown as below.

Find the mean scores.

Solution: