Estimating Population Size


Adjust the number of fish in a lake to be tagged and the number of fish to be recaptured. Use the number of tagged fish in the catch to estimate the number of fish in the lake.

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Assessment Questions (5):

  1. You catch, tag, and release 50 fish back into a pond. Then, you catch 25 more fish, 5 of which have tags on them. What is the best estimate of the number of fish in the pond?
  2. Imagine that a lake contains two kinds of fish: trout and bass. 20% of the fish in the lake are bass and 80% are trout. If you caught 5 fish at random from this pond, which of the following would you expect to catch?
  3. A pond contains 1000 fish, 100 of which have been tagged. You catch 10 fish. How many of them would you expect to be tagged?
  4. Pond 1 contains 100 fish, 50 of which are tagged. Pond 2 contains 1000 fish, 500 of which are tagged. You catch 10 fish from each pond. Which of the following statements is true?
  5. What usually happens to the accuracy of an estimate of population size as the number of fish caught increases?

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