Category: Science > Math
Asked by: mariane0-ga
List Price: $5.00
03 Nov 2003 07:57 PST
Expires: 03 Dec 2003 07:57 PST
Question ID: 272161
If you have n balls, all of different colours, and draw one t times, at random, putting it back afterwards, what is the probability of drawing the red ball r times (out of the t times, order without importance)?
Answered By: mathtalk-ga on 03 Nov 2003 08:32 PST
Hi, mariane0-ga: This is a simple binomial probability. If we ask for the chance of getting the red ball exactly r times out of t draws, then the answer is: C(t,r) * (1/n)^r * (1 - 1/n)^(t-r) where C(t,r) = t!/(r!(t-r)!) is the number of combinations of t things taken r at a time (the familiar binomial coefficient). Please let me know if my answer requires further clarification. regards, mathtalk-ga
rated this answer:
Great, just what I needed to know to compare classifier results. When I asked this question to people who know about classifiers, they didn't know... :-). Thank you very much.
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