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CSIQ

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  1. CSIQ

    One Girl - One Boy

    Hi. I have just read the question and then read some of the forum explainations (only some of them). Many people are getting themselves tangled up. A couple have two kids, one of them is a girl. Assume safely that the probability of each gender is 1/2. What is the probability that the other kid is also a girl? A lot of respondents are adding information that is not in the question. Many talk about biological chances of a second child being this or that. This is immaterial. The question gives the parameters. Each birth has a 1/2 (or 50/50) chance of being a girl or boy. Second. It does not state (or even imply) that the girl is first (or second) born. It merely states 2 kids and one is a girl. Within the framework of the question, the girl is not part of the question (she is a red herring). The question is; what is the chance of the other (not necessarily the second) kid being a girl. As we are told that (for this question) the chance of any birth being 50/50, then the answer is a 50% chance of a girl. The girl/boy, boy/girl argument is mute, because we are not told order of birth, nor are we asked to infer order of birth. So the girl/boy, boy/girl options are, in fact, only one option. Therefore the options are two girls or one of each. And this is purely a 50/50 proposition. I hope this explanation helps sort out the confusion.
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