Capture Recapture

1
Capture Recapture

• A fish farmer estimates the number of fish in
  their breeding tank in the following manner.
• Originally 100 tagged fish were placed in the
  tank. The farmer then catches a sample of fish
  noting the number of tagged and untagged fish.
• This information to estimate the actual fish
  population, by using proportions. The method is
  called Capture-Recapture, and relies on the
  unbiased nature of the recapture.

2
Getting an Answer.

• We need to perform the same calculation for each
  day, and then use the average as our estimate.
• Why would we expect these proportions to be
  equivalent?
• Well, ipso facto, they arent equivalent. Which
  is why we should take more than one sample.
• Random samples, by their nature, are indicative
  but they are not exact.
• They are indicative because the sample is
  indiscriminate
• The sample is assumed to be representative of the
  wider population.