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GCSE Maths: Capture Recapture

Estimate the size of a population from a marked sample. Practise it with adaptive questions for AQA, Edexcel, OCR and Eduqas.

StatisticsFoundation & HigherAQA · Edexcel · OCR · Eduqas

What you need to know

The concepts examiners test on capture recapture, and what each one is really asking.

Write down the capture-recapture proportion
Estimate a population size from the two samples
State the assumptions the method relies on
Recognise when the estimate would be unreliable

Where marks get lost

The exam technique that separates a correct method from a correct answer.

  • Putting the numbers into the proportion the wrong way round
  • Using the number of marked fish recaptured as the sample size
  • Forgetting to state the assumptions when the question asks for them
  • Giving a decimal answer when the population must be a whole number

Capture Recapture questions students ask

Is Capture Recapture on the Foundation paper?

Yes. Capture Recapture appears at both Foundation and Higher tier, though Higher papers take it further.

What should I know before starting Capture Recapture?

It builds on Ratio and proportion and Fractions and Rearranging formulae. If those feel shaky, practise them first — Capture Recapture questions assume them.

What is the most common mistake in Capture Recapture?

Putting the numbers into the proportion the wrong way round.

Which exam boards cover Capture Recapture?

All four we support — AQA, Edexcel, OCR and Eduqas. GCSE Maths subject content is set by the DfE, so the topic is common to every board; what changes is the paper structure and the grade boundaries.