# marginal probability distribution and finding a probability

• Feb 17th 2010, 06:05 PM
ChrisBickle
marginal probability distribution and finding a probability
Im kinda lost on this problem once i figure out the distribution it shouldnt be hard to figure out the probability or independence.

1. Of nine executives in a certain business firm, four are married, three have never married, and two are divorced. Three executives are selected for promotion. Let Y1 be the number of married executives and Y2 be the number of never-married executives among the three selected for promotion. The joint probability distribution of Y1 and Y2 is
f(x,y) = (4chooseX)x(3chooseY)x(2choose3-X-Y)/(9choose3)
where x and y are integers such that 0x3, 0y3, and 1x + y3.
a. Find the marginal probability distribution of X.
b. Find P(X | Y = 2).
• Feb 18th 2010, 01:54 AM
mr fantastic
Quote:

Originally Posted by ChrisBickle
Im kinda lost on this problem once i figure out the distribution it shouldnt be hard to figure out the probability or independence.

1. Of nine executives in a certain business firm, four are married, three have never married, and two are divorced. Three executives are selected for promotion. Let Y1 be the number of married executives and Y2 be the number of never-married executives among the three selected for promotion. The joint probability distribution of Y1 and Y2 is
f(x,y) = (4chooseX)x(3chooseY)x(2choose3-X-Y)/(9choose3)
where x and y are integers such that 0x3, 0y3, and 1x + y3.
a. Find the marginal probability distribution of X.
b. Find P(X | Y = 2).