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To calculate the mean, we divide the sum of the results by the sample size.

Unit 4 - Mean

In this GCSE Biology quiz, you will practise calculating the mean from sets of data and using it to describe patterns in results from experiments and investigations.

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Fascinating Fact:

The mean is most useful when the data are numerical and roughly similar in size. If the values are very spread out, the mean may not represent them well.

In GCSE Biology, you often collect several measurements in an investigation, then calculate the mean. This average helps you compare conditions, discuss reliability and comment on patterns in your data.

Key Terms

Mean: The average value, found by adding all the results together and dividing by how many there are.
Data set: A group of related measurements or observations collected in an experiment.
Outlier: A result that is very different from the others and may be due to error.

Frequently Asked Questions (Click to see answers)

How do you calculate the mean in GCSE Biology experiments?

To calculate the mean, add all of your repeat measurements together, then divide by the number of measurements. Sometimes you may decide to exclude a clear outlier before calculating it.

Why do scientists use the mean instead of just one result?

Scientists use the mean because it reduces the effect of random errors in single readings. Using several measurements and averaging them gives a value that is usually more reliable and representative.

When is the mean not a good summary of a set of results?

The mean is less useful when results vary a lot or include extreme outliers. In those cases, you should also comment on the range or consider using the median to describe the data.

Try These Related Quizzes

1 .

To calculate the mean, we divide the sum of the results by the...

average

sample size

range

statistic

Larger sample sizes give more reliable results

2 .

Average can never be the same value as the maximum unless it is ...

the mean

the minimum

the mode

the median

The other types of average must be less than the maximum

3 .

What is the mode for this data? 11, 11, 13, 13, 11, 14, 11, 11, 12

It is the most common number in the data set

4 .

We can use the mean values of a set of results to ...

plot a scatter diagram

write a hypothesis

draw the diagram

write a risk assessment

Adding a line or curve of best fit then shows the correlation between the variables that have been investigated

5 .

The sample size is the...

range

number of results

mode

graph

You only need a sample size of two to calculate the mean

6 .

Find the mean of the following data: 4, 6, 9, 3, 6

5.4

5.5

5.6

5.7

Sum then divide by the sample size

7 .

Mean is also known as the...

mode

median

average

range

Average is a general word that includes the median and the mode so if you are stating that you are going to work out the average value, strictly speaking you would need to specify which one you intended to use

8 .

The mode is...

the same thing as mean

equal to the average

the number that is repeated most often

the middle value

In some cases, you would be more interested in the mode than the mean

9 .

What is the median for this data? 11, 11, 12, 13, 15, 19, 21

The median is the middle value. The 4th number in the list of 7 numbers in ascending order

10 .

What is the mean for the values: 13, 18, 13, 14, 13, 16, 14, 21, 13

Two thirds of the numbers are less than the average, this shows you how you need to be careful. In an experiment, the values of 18 and 21 could be anomalous results and may need re-checking for accuracy

You can find more about this topic by visiting BBC Bitesize - Practical skills

Author: Donna Davidson (GCSE Biology Teacher & Examiner, Quiz Writer)