Cory Doctorow: Our dangerous statistical ignorance

Re:Cory Doctorow: Our dangerous statistical ignorance by JacobAldridge on Thursday May 22, 2008 @02:05AM (#196947)

I believe the worst damage to statistics is specious reasoning. My favourite chocolate promotion is Mars' '1 in 6 Wins a Free Bar' (on currently here in Oz). If I buy 6 bars, most people would assume I would win once. In fact, I have only a 2/3 chance of winning a free one

1 - (5^6/6^6)

Buy 12 bars, and there's still a more than 10% chance I won't have won yet...most of the chocolate-buying government-voting lottery-praying public would be stunned.

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Re:Cory Doctorow: Our dangerous statistical ignorance by aston on Thursday May 22, 2008 @02:36AM (#196966)

Although the average number of bars you'd need to buy before you win is indeed six. I think almost no one would put the odds of actually winning one by buying six at 100%.

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Re:Cory Doctorow: Our dangerous statistical ignorance by JacobAldridge on Thursday May 22, 2008 @09:18PM (#197711)

"Any 6 bars may not contain a free bar"

You're probably right, and I hope that you are. Still, funny to note that Mars has even put this disclaimer on the bottom of their promo site!

http://www.marsfreebars.com.au/

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Re:Cory Doctorow: Our dangerous statistical ignorance by graywh on Thursday May 22, 2008 @10:01AM (#197122)

And as N approaches infinity, the probability of winning after N tries with a p=1/N approaches 1 - 1/e.

(Proof left to the reader as an exercise.)

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