Capture/Recapture

1
Capture/Recapture

• Imagine you have a population and you want to
  know how big it is BUT it is unrealistic to count
  the animals in the population.

2
A population of fish for example...
3
Take a sample
4
(No Transcript)
5
Count the number in your sample and Mark or Tag
each of them
6
7
7
Release the sample
8
(No Transcript)
9
Give them time to mix with the population.
10
(No Transcript)
11
Now capture a second sample

• Note the proportion of tagged fish in this new
  sample

12
3/10
13
3/10 in the second sample should be approximately
the same as the fraction of the tagged fish in
the population.
That is 3/10 7/population
Now we can solve for the population!