It seems simple, but it isn't
There are a couple of famous counter-intuitive problems in probability theory and the sisters "paradox" is one of them. I'll tell you the problem, let you guess the solution, and then give you some of the background.
Here's the problem: a family has two children. You're told that at least one of them is a girl. What's the probability both are girls?
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Assume that the probability of having a girl or boy is 50% and that the birth order has no effect on the probability. Assume the family is selected at random because they have at least one girl.
What do you think the probability is that both children are girls?
A simpler question
Let's image you're asked a simpler question.
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