Friday, 26 March 2010

pr.probability - Random values and their probability of reoccuring

Call your three questions A, B, C.



The probability that A gets chosen twelve times in a row is 1/(3^12), or 1 in 531441; similarly for B and C.



The probability that some question gets chosen twelve times in a row is thus 3/(3^12), or 1/(3^11), or 1 in 177147.



Personally, I think this seems like low enough a probability that if you knew for sure it actually happened, I'd be suspicious that your code isn't doing what you think it does. But it's also possible that your user really didn't get this question 12 times in a row and is just misremembering.

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