# Math Help - Need Urgent Help!!!!!!!!!

1. ## Need Urgent Help!!!!!!!!!

Can anyone help me with the following problem asap:

There are 9 tennis balls in a box, of which only 5 have not previously been used. Four of the balls are randomly chosen from the box. Let 'z' be the number of new balls among the selected ones:
(a) Find the probability Distribution of z
(b) Evaluate the expectation E(z)
(c) Evaluate the variance Var(z)

Cheers Guys!!!

2. Originally Posted by fk36@le.ac.uk
Can anyone help me with the following problem asap:

There are 9 tennis balls in a box, of which only 5 have not previously been used. Four of the balls are randomly chosen from the box. Let 'z' be the number of new balls among the selected ones:
(a) Find the probability Distribution of z
(b) Evaluate the expectation E(z)
(c) Evaluate the variance Var(z)

Cheers Guys!!!
Read up on the hypergeometric distribution: Hypergeometric distribution - Wikipedia, the free encyclopedia