Which kind of maths panic is worst? When you cannot tell if your answer is correct or not. 0 votes - 0 % When you cannot tell whether you have understood the question or not. 2 votes - 50 % When you cannot answer the question. 0 votes - 0 % When you cannot understand the question. 2 votes - 50 % When the maths is not hard, but the real world implications of the answer are bleak. 1 vote - 25 % 4 Total Votes
It's a stupid question by gazbo (2.00 / 0) #1 Fri Dec 24, 2010 at 10:58:42 AM EST
Or rather, it's a good question asked in a stupid way.  The original phrasing that Google used implies we're modelling this with an infinitely large number of families.  As such, the 50/50 population split answer is fine.

Then this guy's come along and said "fuck it - let's lose that assumption and instead assume a finite number of families."  Which at the face of it may sound reasonable until you realise that the answer then is "I don't know, it depends how many families there are in each country".

Here's an alternative way of asking the question he's asking: "Taking at random a single family using this stopping rule, what's the probability they have more boys than girls?"

That should yield the answer he's after (I think) but without confusing people by making them interpret the problem.  Oh, and it has the benefit that the answer is then an actual number, not a range of values dependent on an unknown variable (number of families) that he's decided to introduce.

I recommend always assuming 7th normal form where items in a text column are not allowed to rhyme.

Expectation of ratios by Alan Crowe (2.00 / 0) #2 Fri Dec 24, 2010 at 02:43:25 PM EST
My suspicion is that taking expected values of ratios is usually a bad idea. Little numerator and little denominator get weighted the same as big numerator and big denominator, while in the real world the big over big is more important. But I want to play with some examples first. Perhaps I'll find time and do that in the new year.

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