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# Geometric Distribution Problem watch

1. I'm stuck on this question. I know you can say that large fish in a pond are geometrically distributed with p = 3/7 which in turn means E(2X) = 2E(X) = 2(1/(3/7)) = 14/3 = 4 2/3, but the answer says it's 5 1/3. I can't understand why - is it a mistake?

Thanks.
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2. (Original post by r3l3ntl3ss)
I'm stuck on this question. I know you can say that large fish in a pond are geometrically distributed with p = 3/7 which in turn means E(2X) = 2E(X) = 2(1/(3/7)) = 14/3 = 4 2/3, but the answer says it's 5 1/3. I can't understand why - is it a mistake?

Thanks.
If you catch a large fish, the probabilities for catching the second large fish are different. You now have two large and four small in the pond.
3. (Original post by Gregorius)
If you catch a large fish, the probabilities for catching the second large fish are different. You now have two large and four small in the pond.
ah yes I see. Even then, you get 7/3 + 6/3 = 13/3 = 4 1/3, not 5 1/3?
4. (Original post by r3l3ntl3ss)
ah yes I see. Even then, you get 7/3 + 6/3 = 13/3 = 4 1/3, not 5 1/3?
Two large fish are left, not three. 7/3 + 6/2 = 5 1/3

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Updated: February 28, 2016
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