STAT 5100 Midterm: STAT 5100 Iowa Midterm1b
Document Summary
Please write your answers in the exam books provided. You can use formulas from page 2 when appropriate: a box contains three drawers. The rst drawer contains two gold coins, the second drawer contains a gold coin and and a silver coin, and the third drawer contains two silver coins. We randomly choose 4 balls from the urn. If 2 of them are white and 2 of them are black, we stop. If not, we replace the balls in the urn and again select 4 balls. 2 of the 4 chosen are white. (a) what is the probability that we make exactly n selections? (b) what is the expected number of selections we make: a random variable x has density fx(x) =( 1. 0 for x > 0 otherwise. and let y = 1/x. (a) find the mean and variance of y . (b) find the density of y : a fair die is rolled n times.
