Capture-Recapture Flashcards

All 4 cards in this deck

What equation is used in the capture–recapture method to estimate a population of size $N$?

$\dfrac{\text{number marked in second sample}}{\text{size of second sample}} = \dfrac{\text{number marked first}}{N}$

What are the steps of the capture–recapture method?

e.g. 20 fish are marked; a later sample of 50 fish contains 4 marked fish

1. Proportion marked in second sample: $\frac{4}{50}$
2. Set equal to the population proportion: $\frac{20}{N} = \frac{4}{50}$
3. Solve: $N = \frac{20 \times 50}{4} = 250$ fish

What assumptions must you state when using the capture–recapture method?

The population has not changed between the samples, the marks are not lost, and the marked members mix back in so each sample is representative.

True or false? In the capture–recapture method the second sample must be the same size as the first sample.

False. The samples can be different sizes; the method compares proportions.