Increasing sample size

Introduce the activity by comparing and contrasting a census and a sample. Discuss the potential impact of varying sample sizes on the reliability of the results gathered from an investigation/survey.

The video Increasing Sample Size shows the changing distributions with increasingly larger samples. You could mute the sound before starting to find out what students are thinking.


You can download the Increasing Sample Size video transcript.


Stop and start the video at appropriate times to pose questions.

Below are some examples of questions you could ask.

  • What do you think will happen if we collect more data?
  • What parts of the graph would you expect to change if more data are added?
  • In what areas of the graph would you expect data to cluster as the sample size grows?
  • How does the distribution of the smaller sample compare with the distribution of the larger population?
  • What is the smallest sized sample needed to be confident it is representative of the larger population?

This activity will establish the value of selecting an appropriate sample size when conducting an investigation.

Curriculum links

Year 8: Investigate techniques for collecting data, including census, sampling and observation

Year 8: Explore the practicalities and implications of obtaining data through sampling using a variety of investigative processes