Shoutbox

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Originally posted by .Roy
Thanks a lot guys =D

Whats the formula for AT LEAST

For example whats the chance of getting AT LEAST 2 out of 5. When the chance of getting it once is 10%

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Easiest way of doing this is working it out for 1 out of 5 trail with a chance of 10% and then taking this away from 100% as this is total probability.

So there are 5 possibilities (for the 1 out of 5 trails) ABBBB BABBB BBABB BBBAB BBBBA

1/10*9/10*9/10*9/10*9/10*5 = 32.805% of it NOT being at least 2 out of 5

100% - 32.805% = 67.195%

Chance of getting at east 2 out of 5 with a chance of getting it once being 10% is 67.195%. (This is so high because it is getting 2 out of 5, 3 out of 5, 4 out of 5 and 5 out of 5)




EDIT: Btw I checked this using my TI83+

And @ Reload2

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Originally posted by Reload2

quote:

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Originally posted by Grue
that probability is 1/10*1/10*1/10*9/10*9/10=81/100000 so 81/100000*10= 81/10000 or .81% chance

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I think that's the same formula that I wrote except I forget to convert to percentage...

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You missed the *10 which makes a big difference, this is because there are 10 different possibilities you can make depending on what order you put it being successful and unsuccessful