Mean, Median and Mode
Laura Armstrong & Joe Wolfensohn
Teachers
Contents
Topic Explainer Video
Check out this @lauradoesGCSEbiology video that explains mean, median and mode, then read the study notes. Once you’ve gone through them, don’t forget to try the practice questions!
Mean, Median and Mode
Understand the terms mean, mode and median and find arithmetic means
An average is a single typical value that is used to represent a set of values.
There are three main types of average. They are called the mean, median and mode.
Mode
- The mode is the value that appears most often in a set of data.
- A data set can have more than one mode (bimodal) or no mode at all.
- Example:
Data: 3, 4, 4, 5, 7, 6
Mode = 4 (appears twice, more than any other number).
Median
- The median is the middle value when data is put in numerical order.
- Example:
Data: 2, 4, 5, 6, 8
Median = 5 (middle number). - If there is an even number of values, take the mean of the two middle numbers.
- Example:
Data: 1, 3, 4, 7
Median = (3 + 4) ÷ 2 = 3.5
Mean
- The mean is used most often in Biology as it uses all values in its calculation.
- The mean is calculated by adding all the numbers and dividing by how many there are.
- Example:
Data: 2, 4, 6, 8
Mean = (2 + 4 + 6 + 8) ÷ 4 = 20 ÷ 4 = 5
What is an anomaly?
- A result that does not fit the pattern of other results - e.g. a repeat that is very different from others.
- Do not include anomalies when calculating the mean.
Example of an Anomaly
|
Repeat |
Result (cm³ of gas) |
|
1 |
12 |
|
2 |
13 |
|
3 |
35 (anomaly!) |
|
4 |
13 |
|
5 |
11 |
Mean = (12 + 13 + 13 + 11) ÷ 2 = 12.3 (The anomaly is left out).
Range
- The range is not an average. It is a measure of how spread out the values are.
- It is calculated by subtracting the lowest value from the highest value.
Practice Question
A student carried out an investigation to see if playing tennis improved reaction time.
The student used two groups of six people. The table below shows the results.
|
Person |
Reaction time in seconds |
|
|
People who play tennis |
People who do not play tennis |
|
|
1 |
0.2 |
0.3 |
|
2 |
0.4 |
0.4 |
|
3 |
0.3 |
0.6 |
|
4 |
0.4 |
0.5 |
|
5 |
0.2 |
0.3 |
|
6 |
0.3 |
0.2 |
|
Mean |
X |
0.4 |
Calculate mean value X in the table above. (2 marks)
Model answer:
(0.2 + 0.4 + 0.3 + 0.4 + 0.2 + 0.3) / 6 = 0.3 seconds
More Practice
Try to answer the practice question from the TikTok video on your own, then watch the video to see how well you did!