It’s so counter-intuitive my head is going to explode.
Here’s the paradox for the uninitiated:If I say, “I have 2 kids, at least one of which is a girl.” What is the probability that my other kid is a girl? The answer is 33.33%.
>*Intuitively, most of us would think the answer is 50%. But it isn’t. I implore you to read more about the problem.*
Then, if I say, “I have 2 kids, at least one of which is a girl, whose name is Julie.” What is the probability that my other kid is a girl? The answer is 50%.
>*The bewildering thing is the elephant in the room. Obviously. How does giving her a name change the probability?*
>
>*Apparently, if I said, “I have 2 kids, at least one of which is a girl, whose name is …” The probability that the other kid is a girl* ***IS STILL 33.33%.*** *Until the name is uttered, the probability remains 33.33%. Mind-boggling.*
And now, if I say, “I have 2 kids, at least one of which is a girl, who was born on Tuesday.” What is the probability that my other kid is a girl? The answer is 13/27.
>*I give up.*
Can someone explain this brain-melting paradox to me, please?
In: 4
>courtesy of u/Tylendal
When you flip two coins, there’s a 25% chance of TT, a 25% chance of HH, and a 50% chance of TH or HT… which is why they’re considered distinct results.
I flipped two coins thirty times and here are the results;
8 flips were both heads (27%)
7 flips were both tails (23%)
15 flips were one of each (50%)
If we consider heads to be boys and tails to be girls, then a boy/girl combo is twice as likely as a combo where the genders match.
With the gender of one of them known it eliminates 25% of the possible combinations, leaving a mixed combo twice as likely as the remaining same gender combo.
Since mixed gender combinations are twice as probable as same gender combinations that leaves a 2:3 chance that the other child is a boy and a 1:3 chance that it is a girl.
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