This refers to the average number, the position or significance of a set of numbers they include;

1. Arithmetic mean (mean x)

This is the sum of all series of scores of the items in the series, that is the average of a given series or scores.

Meanx=∑xn

Where S is the summation of the scores

             X=various number in the series

            N=number of items in the series

Example: What is the mean of the following scores in economics by some form 3 students?

20, 23, 21, 28, 27, 24, 25

Solution

Meanx=∑xn=20+23+21+28+27+24+257=1687=24

Mean(x) = 24

2. The median

This is the middle number of a set of numbers arranged in descending or ascending order of magnitude. If the total number of items in the series is an odd number, the most central number is the median. If the total number of items in the series is an even number, the sum of the two middle numbers is divided by 2 to obtain the median.

Example: Consider the following scores 27, 24, 28, 30, 17, 18 and 20. Calculate the median.

Solution

Re-arrange the scores: 17, 18, 20, 24, 27, 28, 30

The median is 24.

3. The mode

This is a number of score which occurs most frequently in a series. If two numbers occur most frequently the series is Bi-modal.

Example: Consider the series: 30, 40, 50, 30, 60, 70, 40, 80, 30.

Solution

The mode (Mo) = 30.