SOLUTION: A bag contains 22 cubes, of which 11 are red. Three cubes are drawn without replacement. Let X be the number of red cubes drawn. Find the variance of X.

Question 415070: A bag contains 22 cubes, of which 11 are red. Three cubes are drawn without replacement. Let X be the number of red cubes drawn. Find the variance of X.
Answer by robertb(5830) (Show Source): You can put this solution on YOUR website!
The pmf is . Hence
X ----> 0 1 2 3
p(x)--> 0.125 0.375 0.375 0.125
==>
==> .
A shorter solution is as follows: The mean for a binomial experiment is n*p = 3*0.5 = 1.5, while the variance is n*p*q = 3*0.5*0.5 = 0.75. (Here, n = 3, and p = q = 0.5.)
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