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Zaphod Beeblebrox
46499.  Wed Jan 18, 2006 8:30 am Reply with quote

That's ingenious...oh dear, I don't think I'd be very good in these life-threatening situations.

Now, if you're going to be cheeky, I shan't tell you no more.

No cheek intended, I do apologise.

46500.  Wed Jan 18, 2006 8:32 am Reply with quote

Now you're asking me something...

I have two children. They aren't both boys. What is the probability that both children are girls?

If they aren't both boys, the possible pairings of child 1 and child 2 can be:

1=girl, 2=girl
1=boy, 2=girl
1=girl, 2=boy.

The first 'two girls' option is one of three possibilities, so the probability of that is 1/3.

Now suppose that I have two children, of whom the elder is a boy. What is the probability that both are boys?

The other child can be either a girl or a boy. 'Two boys' will be the outcome of one of these two possibilities, so that probability is 1/2.

Thinks: did they buy it?

Mr Grue
46502.  Wed Jan 18, 2006 8:37 am Reply with quote


46506.  Wed Jan 18, 2006 9:26 am Reply with quote

Yes, I suppose it is a bit like the Monty Hall problem, in that there's room for vagueness about 'when' the probability is being measured - before or after you're told some of the pre-conditions.

I think we can also assume that the children are distinguishable (maybe this is why there's a reference to the 'elder' in the second question), in which case BG is not the same case as GB.

46554.  Wed Jan 18, 2006 12:06 pm Reply with quote

It depends if you leave it to chance (slightly greater incidence of females and slightly greater chance of females surviving) or if you allow that environmental influence on gender may be controllable through diet and that there is a tendency to wish to equalise the sex ratio.

46565.  Wed Jan 18, 2006 12:51 pm Reply with quote

Good point Celebaelin, or Garrick could be Chinese in which case the ratio is in boys' favour.

...come to think of it, why are you having 2 children if you're Chinese Garrick? GUARDS, SEIZE HIM.

"....I'm not a guard"

46567.  Wed Jan 18, 2006 12:53 pm Reply with quote


Zaphod Beeblebrox
46574.  Wed Jan 18, 2006 1:12 pm Reply with quote

Perhaps this is why even my internet friends don't like me

Now I'm sure that's not true.

It is a bright, fresh, summer day. A girl is walking across a field. A soldier is moving towards the field, and can see the girl. He knows that when he reaches the field, both he and the girl will die violently, yet he does not stop moving. Why?

Suicide bomber?

Either that or QII's un-opening parachute + explosives dilemma.

Mr Grue
46575.  Wed Jan 18, 2006 1:31 pm Reply with quote

Celebaelin wrote:
It depends if you leave it to chance

Yes and no - the probabilities will still have the same seemingly out of kilter relationship.

46592.  Wed Jan 18, 2006 2:36 pm Reply with quote

Perhaps this is why even my internet friends don't like me.

<Makes garrick a nice, friendly, comforting cup of tea and passes him a home-baked biscuit>


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