Pre-Algebra Chapter 6 - Ramsey School District

A Follow-Up of Lesson 6-2
Capture-Recapture
Scientists often determine the number of fish in a pond, lake, or other body of
water by using the capture-recapture method. A number of fish are captured,
counted, carefully tagged, and returned to their habitat. The tagged fish are
counted again and proportions are used to estimate the entire population.
In this activity, you will model this estimation technique.
Collect the Data
Step 1 Copy the table below onto a sheet of paper.
Step 2 Empty a bag of dried beans into a paper bag.
Step 3 Remove a handful of beans. Using a permanent marker, place an X on
each side of each bean. These beans will represent the tagged fish.
Record this number at the top of your table as the original number
captured. Return the beans to the bag and mix.
Step 4 Remove a second handful of beans without looking. This represents the
first sample of recaptured fish. Record the number of beans. Then count
and record the number of beans that are tagged. Return the beans to the
bag and mix.
Step 5 Repeat Step 4 for samples 2 through 10. Then use the results to find the
total number of recaptured fish and the total number of tagged fish.
Analyze the Data
Original Number Captured:
Sample Recaptured Tagged
1
2
3
4
10
Total
1. Use the following proportion to estimate the number of beans in the bag.
original number captured
total number in bag
2. Count the number of beans in the bag. Compare the estimate to the actual
number.
Make a Conjecture
3. Why is it a good idea to base a prediction on several samples instead of
one sample?
4. Why does this method work?
total number tagged
total number recaptured
Investigating Slope-Intercept Form 275
Algebra Activity Capture-Recapture 275