You are doing a mark-recapture experiment to determine the population size of the MendAliens living on an island in my back yard. Initially, you catch and mark 130 MendAliens, which you then release. Next, you capture 90 MendAliens, of which 20 are marked. What is your estimate of the population size of MendAliens living on the island in my back yard?
[ To get the population size N, multiply the number marked in the first catch, M1, by the total number caught in the second catch, C, and divide that by the number of marked recaptures in the second catch, M2: "N = (M1 x C) / M2" Or: (130 x 90) / 20 = 585 ]