An ornithologist wants to estimate the number of parrots in a large field. She uses a net to catch some, and catches 32 parrots, which she rings and sets free. The following week she manages to net 40 parrots, of which 8 are ringed.
What fraction of her second catch is ringed?
The fraction of the second catch that is ringed is 1/5.
Find an estimate of the total number of parrots in the field.
The estimate of the total number of parrots in the field is 160.
Explanation
This problem is based on the capture-mark-recapture method described in the textbook context. The key assumption is that marked parrots mix uniformly with the remaining parrots, and the sample is a good representative of the entire population. Using ratio and proportion, we can estimate the total population.