, MATH 225N Week 4 Statistics Exam: Probability & Discrete Random Variables
Time Allowed: 90 minutes
Total Points: 100
Instructions: Show all work. Partial credit may be awarded for correct
reasoning. Calculators are allowed.
Section I: Multiple Choice (4 points each, 40 points total)
1. A jar contains 8 red balls, 5 blue balls, and 7 green balls. If one ball is drawn
at random, what is the probability it is not green?
a) 720207
b) 13202013
c) 820208
d) 12202012
2. Events A and B are mutually exclusive.
If P(A)=0.3P(A)=0.3 and P(B)=0.4P(B)=0.4, what is P(A∪B)P(A∪B)?
a) 0.7
b) 0.12
c) 0.58
d) 0.1
3. The probability that a student passes Math is 0.8, and the probability they
pass English is 0.9. If these events are independent, what is the probability
they pass both subjects?
a) 0.72
b) 0.98
c) 0.1
d) 1.7
4. A random variable X has the following distribution:
P(X=1)=0.2,P(X=2)=0.3,P(X=3)=0.5P(X=1)=0.2,P(X=2)=0.3,P(X=3)=0.5
What is E(X)E(X)?
a) 2.0
b) 2.3
c) 2.5
d) 2.1
5. In a binomial experiment with n=10n=10 trials and p=0.4p=0.4, what is the
expected number of successes?
a) 4
Time Allowed: 90 minutes
Total Points: 100
Instructions: Show all work. Partial credit may be awarded for correct
reasoning. Calculators are allowed.
Section I: Multiple Choice (4 points each, 40 points total)
1. A jar contains 8 red balls, 5 blue balls, and 7 green balls. If one ball is drawn
at random, what is the probability it is not green?
a) 720207
b) 13202013
c) 820208
d) 12202012
2. Events A and B are mutually exclusive.
If P(A)=0.3P(A)=0.3 and P(B)=0.4P(B)=0.4, what is P(A∪B)P(A∪B)?
a) 0.7
b) 0.12
c) 0.58
d) 0.1
3. The probability that a student passes Math is 0.8, and the probability they
pass English is 0.9. If these events are independent, what is the probability
they pass both subjects?
a) 0.72
b) 0.98
c) 0.1
d) 1.7
4. A random variable X has the following distribution:
P(X=1)=0.2,P(X=2)=0.3,P(X=3)=0.5P(X=1)=0.2,P(X=2)=0.3,P(X=3)=0.5
What is E(X)E(X)?
a) 2.0
b) 2.3
c) 2.5
d) 2.1
5. In a binomial experiment with n=10n=10 trials and p=0.4p=0.4, what is the
expected number of successes?
a) 4
