Something Fishy
Statistics
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Objective
Students will estimate the size of a large population by applying the concepts of ratio and
proportion through the capture-recapture statistical procedure.
Overview of the Lesson
Students are introduced to a problem involving an environmental issue: scientists have
determined that the number of fish in the Chesapeake Bay has decreased. Assuming that
this is true, scientists must have counted the number of fish and noted the change. How
did they count the fish? Groups are formed to explore a wide range of possible strategies.
Students are introduced to the capture-recapture method which involves capturing fish,
tagging them, returning them and recapturing another sample. In groups, students are
given containers (the bay) and an unknown number of fish-shaped cheese crackers to use
in simulating the capture-recapture method. Students net the fish-shaped cheese crackers
and substitute fish-shaped pretzels to simulate tagged fish. Groups then take samples and
record the number of tagged fish and the total number of fish. After several samples are
taken, results from each group are recorded. Students apply their knowledge of proportion
to arrive at the total fish population.
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