GB-30-04-001 · Capture–recapture
A researcher marks 109 beetles and releases them. Later, a random sample of 36 beetles contains 15 marked beetles.
(a) Estimate the population. Give your answer to the nearest whole number.
(b) State one assumption needed for this estimate.
Part (a)
Tagged / Capture–Recapture Sampling
Booklet p. 22
Method
1) Let N = total population
2) Equate tagged fractions (Total / Sample): tagged_total / N = tagged_in_sample / sample_size
3) Cross multiply and solve
Worked Example (GB-30-04-001 · Part (a))
Estimate the population. Give your answer to the nearest whole number.
Booklet p. 22 — Set up and cross-multiply ():
1) Use 109/N = 15/36.
2) 262
262
Part (b)
Tagged / Capture–Recapture Sampling
Booklet p. 22
Method
State an assumption needed for the proportional model
Worked Example (GB-30-04-001 · Part (b))
State one assumption needed for this estimate.
1)
The marked beetles have mixed randomly with the population.
2)
The sample must represent the whole population for its marked fraction to estimate the population marked fraction.
Ans =
The marked beetles have mixed randomly with the population.