A lake contains 200 trout; 50 of them are caught, tagged and returned to the lake.Suppose we catch 40 trout at random a few days later, what is the probability that 10 ofthem are tagged?
suppose 10 are tagged can be selected from 50 tagged trout, then remaining 40 - 10 = 30 untagged trout can be selected from 200 - 50 = 150 trout.
And total 40 trout can be selected from 200 trouts.
Therefore if we catch 40 trout at random a few days later then the probability that 10 ofthem are tagged is,
Probability = 0.161331
Note: Above question is a application of Hypergeometric distribution. So, using excel we can find this probability,
Excel Command:
=HYPGEOMDIST(10, 40, 50, 200) = 0.16133141
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