Question

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?

A. 130
B. 234,000
C. 29
D. 14
E. 585

Answer 1

E

Explanation:

When you perform an experiment on a population, the majority of the time, you cannot use the entire population, so instead you use a sample of that population.

In this case, you mark 130 MendAliens out of an unknown population. After that you capture 90, and see that 20 are marked. You can use this to assume that for every 90 MendAliens, you marked 20, so if you calculate that as a percentage, you would get 22.22%.

This means that you marked approximately 22% of the population, when you marked those 130 MendAliens. Using basic math, we can work backwards to calculate the total population.

Percentage (%) = Sample / Total

Inserting the values we know...

22.22% = 130 / Total

Rearranging the formula, we get...

Total = 130 / 22.22%

Since we know 22.22% is actually equal to (22.22 / 100)= 0.2222

Total = 130 / 0.2222

Total = 585