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Jan. 22nd, 2010 12:12 pm
jack: (Default)
[personal profile] jack
What all this Leno/Conan/Late Night Gubbins is about: a primer for friends in the UK

http://littleredboat.co.uk/?p=3132

You may recently have seen people complaining about... some row that went on between Jay, um, Leno and Conan O'Brian on some kind of late-night talk show aired in America. For that matter, you might have seen references to said late night talk shows in general, and be in the situation for which we need a word of "OK, so it's a late night talk show. What's it good at? What's it famous for?"

The linked post does a lovely job of explaining why the row was very, very entertaining, even if you don't normally want to read about dick-waving contests between people you've barely heard of.

"And so began a monumental game of chicken. Conan went onto his show every night subsequently, and did monologues that consisted entirely of calling his network useless, unpopular, incapable of running itself - of calling its executives liars and thieves, and calling Leno all manner of other things"

"it has been, for a brief time, a remarkable insight on the workings of it all - and the true bitterness, fear and anger present in all parts of the industry (of most similar industries) right now."

People with Exactly Two Children and At Least One Daughter, what's the gender make-up of your kids

There's a well-known paradox[1] in statistics, which goes that "suppose you know Mrs Smith has two children, and you see something that suggests that (at least) one of them is a girl. What are the chances that the other one is a boy?"

People instinctively say "50/50"[2]. But in fact, it's 2/3.

This is because there 50% of families have mixed children, 25% two girls, and 25% two boys, so there are twice as many boy/girl families as girl/girl families. You can see this easily if you agree the first child was 50/50 boy/girl, and so boy followed by girl and boy followed by boy are both 25%, as are the other two possibilities.

What's funny is that here: http://boards.straightdope.com/sdmb/showthread.php?t=548550 someone acknowledged that this may not be intuitive to everyone, so made a poll which actually asked people to respond if they had two children, at least one a girl, and say which make-up their family had. It's so much more convincing to see the poll made of actual people, actually showing a 2:1 ratio[3].

PS. Note that this result depends very heavily on finding out by coincidence that one of the children is a girl. A very slight change in wording can make it refer to a situation where the chance IS 50/50, and a very slight change in wording can make it much much more or less obvious which answer is right. In fact, I probably got the wording wrong in my quote, so if you still think it's wrong, it could be that you are right, and my reasoning only applies to the problem I meant to describe.

If you think you've got it understood, next read about the http://en.wikipedia.org/wiki/Monty_Hall_problem with the goats.

Footnote #1: on paradox

Paradox is typically used to mean "an apparently contradictory result". Sometimes this is an ACTUALLY contradictory result, such as "we know time-travel can't allow X because even if we don't know what's physically possible, that's actually self-contradictory". Sometimes this is contradictory because an underlying assumption was subtly false. Sometimes it contradicts what you think OUGHT to be true. In statistics, most paradoxes are of the last sort: all the maths line up, but it superficially looks impossible.

Footnote #2

In these sorts of problems, the aim is to distinguish between two grossly different results stemming from different understandings of the problem. Thus all the actual numbers are approximate: the argument works equally well even though the actual chance of boy/girl is several percent different from 50.

Date: 2010-01-22 01:50 pm (UTC)
naath: (Default)
From: [personal profile] naath
Is there a footnote 3?

A very slight change in wording can make it refer to a situation where the chance IS 50/50

I believe you have it right. If you discover that at least one child of two is a girl there is a 2/3 chance that the other is a boy; however if you discover that the older of two children is a girl then there is a 1/2 chance that the younger is a boy.

[most stats books I have read this in have some stupid 'finding out' thing; relying on crud like "pink stuff is for girls". But supposing you were using rather better information...]

And don't talk to me about goats.
Edited Date: 2010-01-22 01:52 pm (UTC)