PSTAT 5A
Unit 2 Practice Problems
1. An urn contains 12 blue and 2 white marbles. 3 are chosen at random, and
we are interested in counting the number of white marble.
Define the random variable, X =
A. Find P(X = 0)
B. Find P(x = 2)
2. Construct the PDF and CDF for X in problem 1.
3. Find the expected value and standard deviation of X.
4. A box contains fifty $1 bills and two $100 bills. Two bills are chosen at
random. Let X = the amount of money won.
Construct the PDF for X. If you had to pay $10 to play this game, would you
play? Use the concept of Expected Value and Standard Deviation to explain
your answer.
5. Below is a PDF for a random variable, X.
X 0 2 3 6
P(X = x) 0.10 a 0.65 0.15
A. Find a.
B. Find P(X ≤ 3)
C. Find the standard deviation of X.