Instructor: Lam, H. Sta 120 MW 4-5:50pm
Quiz 2 Review
CHAPTER 5
1. Give 2 examples of each, discrete random variable and continuous random variable. (4 pts)
2. Verify if the table (A, B, C) represents a valid probability distribution. Explain. (2 pts each)
A
B
C
x
P(x)
0
.10
1
.22
2
.40
3
.28
x
P(x)
2
.04
3
.37
4
.21
5
.12
x
P(x)
7
.43
8
.68
9
-
.11
3. Given the following probabilities distribution of a discrete random variable x. (2 pts each)
x
0
1
2
3
4
5
P(x)
.19
.35
.24
.12
.06
.0
4
a. What is the probability that x is at most 3?
b. The probability that x is at least 4 is?
c. If x is exactly 2, what should the probability be?
d. Compute > 5
e. Find < 2
4. What are the formulas of the mean and standard deviation of a discrete random var.? (2 pts)
5. Find the expected value (or mean) and standard deviation for #2 above? (2 pts)
6. Evaluate the following factorials: (2 pts each)
a. 8! b. (2 - 1)! c. 0! d. (12-3+1-6)! e. n!
7. Given that there are 10 problems on a Math exam. If you randomly selected 6 problems out of
the 10, how many different combinations are there to choose from? (3 pts)
8. What are the 4 conditions of a Binomial probability distribution? Give one example and explain
why it satisfies the properties of Bernoulli. (5 pts)
9. Write and clarify the formula of a Binomial probability distribution. (2 pts)
10. For any number of n trials, when is the Binomial probability distribution symmetric? When is it
skewed to the right? When is it skewed to the left? [Hint: something about p] (3 pts)
11. A university computer break down an average 2.1 times a month. Find the probability that
during the next month this computer will break at least 6 times. Use the Poisson probability
table or use the Poisson formula to figure this out. (2 pts)
12. On an average, 2 out of every 15 students give up on trying per quarter in a P.E. class. What is
the probability that exactly 6 of 45 students gave up trying in that particular class? (2 pts)
13. What are the man, variance, and standard deviation of a Poisson prob. Distribution? (3 pts)
14. Give an example of a Poisson probability distribution. (1 pts)
15. Explain the 3 conditions of a Poisson probability distribution. (3 pts)
