An average is a
single number which is used to represent a collection of numerical
data. An average is a single value that is meant to typify a list
of values. If all the numbers in the list are the same, then this
number should be used. If the numbers are not all the same, an easy
way to get a representative value from a list is to randomly pick
any number from the list. However, the word average is usually
reserved for more sophisticated methods that are generally found
to be more useful.
There are various
types of average. Three averages which are commonly used are the
mean (or arithmetic mean), the median, and the mode. These are defined
and illustrated using the following example.
In a skittles match Tina scored 6, 5, 8, 12, 3, 5, 7, 7, 5
in her nine goes.
The mean is obtained by dividing the sum of all the data by
the number of data.
(6 + 5 + 8 + 12 + 3 + 5 + 7 + 7 + 5) ÷
This gives the
mean as 6.44 to 2 decimal places. Note that this number is not obtainable
as a score, but it represents Tina’s skill at skittles on
The median is the
middle score if the scores are put in order of size 3 5 5 5 6 7 7 8
The middle score
in this set of data is the 5th number along, namely 6, so 6 is the
median score. If there were an even number of scores, the median
would be taken as the mean of the middle two scores.
The mode is the
number which occurs most often. In this example 5 is the most frequently
occurring score, so 5 is the mode.