Basic probability problem

A

AbdelRahmanShady

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Lets say there are two whales and I tell you one of them is whale male. What is probability that the other is male.
The solution is that the sample space is (male, male), (male, female), (female, male) all are equally likely so answer is 1/3 and I checked by doing a simulation.
The problem is the other proof that came to me. We know the that one of them is male so it should be first one or second.
If it is first the second one has 1/2 of being male ,and if the male whale was second the first one has also 1/2 of being whale, so answer is 1/2 which is clearly wrong but why.
 
AbdelRahmanShady said:
Lets say there are two whales and I tell you one of them is whale. What is probability that the other is male.
The solution is that the sample space is (male, male), (male, female), (female, male) all are equally likely so answer is 1/3 and I checked by doing a simulation.
The problem is the other proof that came to me. We know the that one of them is male so it should be first one or second.
If it is first the second one has 1/2 of being male ,and if the male whale was second the first one has also 1/2 of being whale, so answer is 1/2 which is clearly wrong but why.
Click to expand...
The gender of the first whale has no effect whatsoever on the second whale. The probability is 50%!
if you throw a coin, and get a heads, what is the probability that the second throw will be heads? The coin doesn’t “know” what happened just now, the throws are independent. It’s the same here!
 
AbdelRahmanShady said:
Lets say there are two whales and I tell you one of them is whale. What is probability that the other is male.
The solution is that the sample space is (male, male), (male, female), (female, male) all are equally likely so answer is 1/3 and I checked by doing a simulation.
The problem is the other proof that came to me. We know the that one of them is male so it should be first one or second.
If it is first the second one has 1/2 of being male ,and if the male whale was second the first one has also 1/2 of being whale, so answer is 1/2 which is clearly wrong but why.
Click to expand...
If you know the first whale is a male, then (female, male) is not a valid outcome in your sample space.
 
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