Introduction

We all use the word ‘average’ quite loosely, as part of our normal vocabulary.  There are, in fact, several different measure that can be used to give a single summary measure of a set of data.  It is important, therefore, to be precise when using the word ‘average’ so as to avoid misunderstandings.

In quoting an ‘average’ we are attempting to summarize the distribution with one central measure, so the averages are often referred to as measures of location or measures of central tendency

Five commonly used measures are:

• Arithmetic mean
• Median
• Mode
• Geometric means
• Harmonic mean

Details of how to calculate these averages are given in the texts. There is no need to spend too much time on studying the detailed calculations, since we will do the calculations on a spreadsheet or with a calculator.

Choosing which average to use
There is no ’best’ measure to use. Any one we choose will depend on:

• the type of data and its distribution
• the use we wish to make of the measure