Capture Recapture
Teach Genie
Review Capture Recapture by teaching Genie
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Capture recapture is used when a population is too large or hidden to count directly. You take a first sample, mark it, release it, then later take a second sample and see how many marked individuals are found again.
The population is the whole group you want to estimate, and a sample is a smaller group taken from it. The key idea is that the proportion marked in the second sample should reflect the proportion marked in the whole population.
If only a few of the second sample are marked, the total population is probably large. If many are marked, the total population is probably smaller.
Question 1
3 marksBhavna has a bag containing a large number of beads.
She wants to find an estimate for the number of beads in the bag.
Bhavna takes a sample of 30 beads from the bag.
She marks each bead with a black cross.
She then puts the beads back in the bag.
Bhavna shakes the bag.
She now takes another sample of 30 beads from the bag.
4 of these beads have been marked with a black cross.
What is capture recapture used to estimate?
Capture Recapture Revision Guide
Revision notes for CCEA GCSE Maths Capture Recapture: explanations and worked examples.