Author: Serge Desmarais
Date: 20:30:44 08/28/98
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On August 18, 1998 at 07:26:14, fca wrote: ut I didn't answer (c). >I already gave an example of a *bad question* (I repeat, with some >simplification): > >Given: A child may be only a boy (B) or a girl (G). Twins and higher do not >occur. Bs and Gs are equiprobable. The sex of any existing child does in no >way affect the probability of the sex of its later-born sibling or half-sibling >being B or G. >A man has exactly two biological children. >Question (1): "One of them is a B. What is the probability that both are Bs?" >Question (2): "The older of them is a B. What is the probability that both are >Bs?" > >Now the answer to (1) is 1/3, and to (2) is 1/2. I don't understand how you can say that the answer to 1 is 1/3? If the first one is a boy, the other child has 50% chance of being a boy and 50% of being a girl, so that should be 1/2, instead! Serge Desmarais > >In computer-chess > >Kind regards > >fca > >PS: Yes I can count. The mathematician was a woman. > >;-)
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