2h.02 Apply Petersen capture recapture formula to calculate an estimate of the size of a... Quiz: Pearson Edexcel Statistics, Unit 2

The 20 questions

1. What does the Petersen capture-recapture formula calculate an estimate of?

   • Sample mean
   • Population size
   • Probability
   • Median height

2. In the Petersen formula, what does n1 represent?

   • First sample size
   • Second sample size
   • Total population
   • Marked recaptures

3. In the Petersen formula, what does m represent?

   • Population size
   • Total marked
   • Marked recaptures
   • Second sample size

4. Which key assumption is required for the Petersen capture-recapture method?

   • Random mixing
   • No births
   • Fixed median
   • Equal samples

5. Which assumption means no individuals enter or leave the population between captures?

   • A stratified population
   • A random population
   • An open population
   • A closed population

6. What happens to the first sample in capture-recapture before the second sample?

   • Destroyed
   • Kept in captivity
   • Measured only
   • Marked and released

7. Which term is used for the formula that estimates population size from two samples?

   • Binomial probability formula
   • Standard deviation formula
   • Petersen capture-recapture formula
   • Pearson correlation formula

8. What is the appropriate unit for a Petersen population estimate?

   • Probability
   • Mean score
   • Percentage
   • Number of individuals

9. 100 fish were caught and marked. A later catch of 80 contains 16 marked fish. What is the estimated population?

   • 180
   • 16
   • 500
   • 1600

10. 50 birds were marked in the first sample. The second sample has 60 birds, of which 15 are marked. What is the estimate?

    • 75
    • 150
    • 200
    • 2000

11. A first sample of 30 is marked. A second sample of 45 contains 9 marked. What is the Petersen estimate?

    • 150
    • 54
    • 270
    • 135

12. Why does a larger second sample typically improve a Petersen estimate?

    • Reduces population
    • Removes bias
    • Stops migration
    • More recaptures found

13. The population estimate is 300. The first sample marked 60 individuals and the second sample has 75 individuals. How many marked individuals should the second sample contain?

    • 12
    • 15
    • 20
    • 45

14. If fewer marked individuals are found in the second sample, what happens to N?

    • Estimate decreases
    • Becomes zero
    • Stays the same
    • Estimate increases

15. 240 fish are marked. A second catch of 200 contains 40 marked fish. What is the estimate?

    • 1200
    • 960
    • 240
    • 2400

16. What is the effect on the Petersen estimate if marks are lost between samples?

    • Unchanged
    • Exact
    • Too small
    • Too large

17. A closed population has 1000 members. 100 are marked in the first sample and the second sample has 100 members chosen at random. How many marked individuals are expected in the second sample?

    • 1
    • 10
    • 50
    • 100

18. Why is random mixing important in the capture-recapture method?

    • Reduces sample size
    • Speeds up survey
    • Guarantees closure
    • Prevents selection bias

19. A student uses (n1 + n2) / m instead of n1 x n2 / m with n1 = 60, n2 = 40 and m = 8. Which is the correct Petersen estimate?

    • 480
    • 300
    • 2400
    • 12.5

20. What does a valid Petersen capture-recapture estimate rely upon?

    • Equal samples
    • Zero mortality
    • Complete census
    • Reasonable assumptions

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