On Sep 30, 2010, at 7:56 PM, Joel N. Fischoff wrote:

> Here's the deal: I want to randomly generate a number between 3 and 10.  Is
> it more probable that I will get a higher number if I generate the number
> directly (i.e. between one and ten, and ignoring if I get one or two), or
> if I generate it indirectly (by generating a number between one and eight
> and adding two).  It seems more likely that the latter would generate
> higher numbers more probably, because the chance of generating any given
> number (between one and eight) is 12.5%, while the former is 10% even.  Am
> I right, wrong, or it just doesn't make one bit of difference?


        The distribution would be the same, but the efficiency of the 1:10 
scheme is worse. While it looks like a 10% chance, remember that 20% of the 
time the number will be discarded and a new number generated, with a 20% chance 
that that will be discarded, etc.. The net result is that for each "accepted" 
number, the odds will be 12.5% for each. You will have an 8.5% "do-over" rate, 
which is why the 1:10 scheme is less efficient than the 3:10 scheme.



-- Ed Leafe




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