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**JaguarXJS** Case (1) Suppose I meet you on the street corner, I introduce you to my son and inform you that I have another child. The probability that my other child is a girl is 2/3

Case (2) Now suppose I meet you on the street corner, I introduce you to my 1st born (or 2nd born) son and inform you that I have another child. The probability that my other child is a girl is 1/2

Now suppose in case 2, because of the noise in the streets, you did not hear me state that this son was my 1st born.

This is where I get confused. Whether I had said 1st born or 2nd born the probability that the other child is a girl is 1/2.

However, if you did not hear me say whether this son is my 1st or 2nd born child, then this is exactly like case 1 and the p(other child is a girl)=2/3.

What am I missing here???!!!