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Samples and populations

  • The population is the entire collection of units about which we would like to ask questions, draw information and make claims.
  • The sample is the collection of units that is actually measured or classified.
  • A case is single object or individual to be measured (if numerical) or classified (if categorical).

Although any subset of a population can be considered as a sample, the purpose of the sample is to be representative of the population. The sample should be a small-scale replica of the population. In this way, any claims based on the sample can also confidently be made about the population.

A sample should be carefully planned in the context of the question being asked.

Mystery bag

In this classroom activity, students draw a sample from a bag of tiles and try to predict the contents of the bag. 

Curriculum links

Year 8: Explore the variation of means and proportions of random samples drawn from the same population

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