Add the numbers together and divide the total by the amount of numbers.
The mean for this example is:
You can write a mean as a decimal number or round to a whole number.
Kieran only had 11 results, so calculating the mean in this way was not too time consuming or complicated.
Finding the mean from a frequency tableIf Kieran had 111 CDs, it is likely that he would have made a mistake while typing the results into his calculator. In cases like this, finding the mean from a frequency table is more efficient.
Work through an example in the activity below to practise reading information from a frequency table. The medianThe median is the middle number. To calculate the median of any set of numbers, you need to write the numbers in order.
To find the median number:
Put all the numbers in numerical order.
If there is an odd number of results, the median is the middle number.
If there is an even number of results, the median will be the mean of the two central numbers.
Finding the median with an odd number of resultsUsing the same example, find the median number of tracks on Kieran's CDs.
Kieran's results were:
9 13 9 11 9 13 11 9 10 8 11
Put the numbers in numerical order:
8 9 9 9 9 10 11 11 11 13 13
Find the middle number:
8 9 9 9 9 10 11 11 11 13 13
The middle number is 10, so the median is 10.
Finding the median with an even number of resultsTo find the median of the numbers: 5 11 12 4 8 21.
Put the results in order:
4 5 8 11 12 21.
Find the middle number or numbers:
4 5 811 12 21.
If there are two central numbers, we need to find their mean.
The median is therefore:
(8 + 11) ÷ 2 = 9.5The modeThe mode is the number which occurs most often in a set of data. There can be more than one mode.
Have another look at Kieran's results and find the mode:
9 13 9 11 9 13 11 9 10 8 11
We need to identify the number that appears in this set of numbers the most. Sometimes it helps to list the numbers in numerical order:
8 9 9 9 9 10 11 11 11 13 13
Here we can see that the number 9 occurs most often, so 9 is the mode.
From a frequency table, it is even easier to spot the mode.