Posted on 06/29/2010 4:35:59 AM PDT by mattstat
I have two children, one of whom is a son born on a Tuesday. What is the probability that I have two boys?
The probability is not 1/2!
(Excerpt) Read more at wmbriggs.com ...
Yeah, it is.
Good problem for an actuary...too early in the morning for me.
Nope. It’s about 0.48.
Your probability is 100%, or 1.
It’s an easy problem. Write out the possibilities.
Good article; thanks for posting!
Nevermind. I misread the problem. I thought the question was what is the probability you have one son, and the answer was in the question.
It’s all about how you ask the question.
Ah, but what is probability of double-posting?
Start with the fact it is a Poisson Distribution...
If your son was born last Tuesday, the probability you have two sons is 2/3.
Complete baloney! The author correctly states that, for probability calculations, “The first—and most important—rule of counting is this: What is everything that can happen? In the “Mrs Smith” problem, given the information provided, everything that can happen is this:
Boy, Girl
Girl, Boy
Boy, Boy.”
The list should include all the DIFFERENT possibilities. Possibilities 1 and 2 are the same for purposes of the problem. Therefore the probability is (close to) 1/2, not 1/3.
It doesn’t say “only” one born on Tuesday.
.
You are very blessed, at least until they reach their teens and college ages.
In my case, it is.
But how about Mr B? Here’s a twist: Mr B has two children, one of whom is a son born on 29 June. What is the probability that Mr B has two boys?
If you had one child on a tuesday, and it was a boy, the odds that a second child born would be a boy would be one in two. The probability of a future event is not affected by a past event.
But that’s not what this topic is about. What we’re asking is “of those families with two children and at least one boy, how many have two boys?” There are two possibilities for one girl and one boy (first child is a girl, or the second child is a girl), and only one possibility for two boys.
No, they’re no different possibilities. You don’t know birth order.
No, the article is playing with you. It’s 1/3.
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