Chapter 06 Page 1 of 5
WebQuizzing – Ch.06
Book ISBN-10 0538477490
Book ISBN-13 9780538477499
Author: Gerald Keller
Title: Statistics for Management and Economics
Ed: 9e
# Questions Submitted: 21 Multiple Choice
1. The weighted average of the possible values that a random variable X can assume, where the
weights are the probabilities of occurrence of those values, is referred to as the:
A. variance.
B. standard deviation.
C. expected value.
D. None of these choices.
Analysis:
A. Incorrect. They are referred to as expected value.
B. Incorrect. They are referred to as expected value.
C. Correct. They are referred to as expected value.
D. Incorrect. They are referred to as expected value.
ANSWER: C Ref: Section 6.1
2. The number of accidents that occur annually on a busy stretch of highway is an example of:
A. a sample space.
B. a probability distribution.
C. a random variable.
D. None of these choices.
Analysis:
A. Correct. This is an example of a sample space.
B. Incorrect. This is an example of a sample space.
C. Incorrect. This is an example of a sample space.
D. Incorrect. This is an example of a sample space.
ANSWER: A Ref: Section 6.1
3. Which of the following is a discrete random variable?
A. The Dow Jones Industrial average.
B. The volume of water in Michigan Lakes.
C. The time it takes you to drive to school.
D. The number of employees of a soft drink company.
Analysis:
A. Incorrect. The number of employees of a soft drink company is a discrete random variable.
B. Incorrect. The number of employees of a soft drink company is a discrete random variable.
C. Incorrect. The number of employees of a soft drink company is a discrete random variable.
D. Correct. The number of employees of a soft drink company is a discrete random variable.
ANSWER: D Ref: Section 6.1
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4. Which of the following is a continuous random variable?
A. The number of employees of an automobile company.
B. The amount of milk produced by a cow in one 24-hour period.
C. The number of gallons of milk sold at Meijer grocery store last week.
D. None of these choices.
Analysis:
A. Incorrect. The amount of milk produced by a cow in one 24-hour period is a continuous
random variable.
B. Correct. The amount of milk produced by a cow in one 24-hour period is a continuous random
variable.
C. Incorrect. The amount of milk produced by a cow in one 24-hour period is a continuous
random variable.
D. Incorrect. The amount of milk produced by a cow in one 24-hour period is a continuous
random variable.
ANSWER: B Ref: Section 6.1
5. A function or rule that assigns a numerical value to each simple event of an experiment is
called:
A. a sample space.
B. a probability distribution.
C. a random variable.
D. None of these choices.
Analysis:
A. Incorrect. It is called a random variable.
B. Incorrect. It is called a random variable.
C. Correct. It is called a random variable.
D. Incorrect. It is called a random variable.
ANSWER: C Ref: Section 6.1
6. If X and Y are random variables, the sum of all the conditional probabilities of X given a
specific value of Y will always be:
A. 0.0
B. 1.0
C. the average of the possible values of X.
D. the average of the possible values of Y.
Analysis:
A. Incorrect. Probabilities of X given a specific value of Y will always be 1.0
B. Correct. Probabilities of X given a specific value of Y will always be 1.0
C. Incorrect. Probabilities of X given a specific value of Y will always be 1.0
D. Incorrect. Probabilities of X given a specific value of Y will always be 1.0
ANSWER: B Ref: Section 6.1
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Page 3 of 5
7. Which of the following is not a characteristic of a binomial experiment?
A. There is a sequence of identical trials.
B. Each trial results in two or more outcomes.
C. The trials are independent of each other.
D. The probability of success p is the same from one trial to another.
Analysis:
A. Incorrect. Each trial results in two or more outcomes is not a characteristic.
B. Correct. Each trial results in two or more outcomes is not a characteristic.
C. Incorrect. Each trial results in two or more outcomes is not a characteristic.
D. Incorrect. Each trial results in two or more outcomes is not a characteristic.
ANSWER: B Ref: Section 6.2
8. The expected value, E(X), of a binomial probability distribution with n trials and probability
p of success is:
A. n + p
B. np(1-p)
C. np
D. n + p - 1
Analysis:
A. Incorrect. np is the expected value, E(X).
B. Incorrect. np is the expected value, E(X).
C. Correct. np is the expected value, E(X).
D. Incorrect. np is the expected value, E(X).
ANSWER: C Ref: Section 6.2
9. The variance of a binomial distribution for which n = 100 and p = 0.20 is:
A. 100
B. 80
C. 20
D. 16
Analysis:
A. Incorrect. The variance is 80
B. The variance is 80
C. Incorrect. The variance is 80
D. Correct.
ANSWER: D Ref: Section 6.2
10. Which of the following about the binomial distribution is not a true statement?
A. The probability of success must be constant from trial to trial.
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B. Each outcome is independent of the other.
C. Each outcome may be classified as either “success” or “failure”.
D. The random variable of interest is continuous.
Analysis:
A. Incorrect. The random variable of interest is continuous is not a true statement.
B. Incorrect. The random variable of interest is continuous is not a true statement.
C. Incorrect. The random variable of interest is continuous is not a true statement.
D. Correct. The random variable of interest is continuous is not a true statement.
ANSWER: D Ref: Section 6.2
11. The Poisson random variable is a:
A. discrete random variable with infinitely many possible values.
B. discrete random variable with finite number of possible values.
C. continuous random variable with infinitely many possible values.
D. continuous random variable with finite number of possible values.
Analysis:
A. Correct. The Poisson random variable is a discrete random variable with infinitely many
possible values.
B. Incorrect. The Poisson random variable is a discrete random variable with infinitely many
possible values.
C. Incorrect. The Poisson random variable is a discrete random variable with infinitely many
possible values.
D. Incorrect. The Poisson random variable is a discrete random variable with infinitely many
possible values.
ANSWER: A Ref: Section 6.3
12. Which of the following cannot have a Poisson distribution?
A. The length of a movie.
B. The number of telephone calls received by a switchboard in a specified time period.
C. The number of customers arriving at a gas station in Christmas day.
D. The number of bacteria found in a cubic yard of soil.
Analysis:
A. Correct. The length of a movie cannot have a Poisson distribution.
B. Incorrect. The length of a movie cannot have a Poisson distribution.
C. Incorrect. The length of a movie cannot have a Poisson distribution.
D. Incorrect. The length of a movie cannot have a Poisson distribution.
ANSWER: A Ref: Section 6.3
13. In a Poisson distribution, the:
A. mean equals the standard deviation.
B. median equals the standard deviation.
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C. mean equals the variance.
D. None of these choices.
Analysis:
A. Incorrect. In a Poisson distribution, the mean equals the variance.
B. Incorrect. In a Poisson distribution, the mean equals the variance.
C. Correct. In a Poisson distribution, the mean equals the variance.
D. Incorrect. In a Poisson distribution, the mean equals the variance.
ANSWER: C Ref: Section 6.3
14. A community college has 150 person computers. The probability that any one of them will
require repair on a given day is 0.025. To find the probability that exactly 25 of the
computers will require repair, one will use what type of probability distribution?
A. Binomial distribution
B. Poisson distribution
C. Normal distribution
D. None of these choices.
Analysis:
A. Correct. This is the type of probability distribution one will use.
B. Incorrect. This is the type of probability distribution one will use.
C. Incorrect. This is the type of probability distribution one will use.
D. Incorrect. This is the type of probability distribution one will use.
ANSWER: A Ref: Section 6.2