Chapter 07
Page 1 of 5
WebQuizzing – Ch.07
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. Which of the following represents a difference between continuous and discrete random
variables?
A. Continuous random variables assume an uncountable number of values, and discrete
random variables do not.
B. The probability for any individual value of a continuous random variable is zero, but for
discrete random variables it is not.
C. Probability for continuous random variables means finding the area under a curve, while
for discrete random variables it means summing individual probabilities.
D. All of these choices are true.
Analysis:
A. Incorrect. All of these choices are true.
B. Incorrect. All of these choices are true.
C. Incorrect. All of these choices are true.
D. Correct. All of these choices are true.
ANSWER: D Ref: Section 7.1
2. Which of the following is always true for all probability density functions of continuous
random variables?
A. The probability at any single point is zero.
B. They contain an uncountable number of possible values.
C. The total area under the density function f(x) equals 1
D. All of these choices are true.
Analysis:
A. Incorrect. All of these choices are true.
B. Incorrect. All of these choices are true.
C. Incorrect. All of these choices are true.
D. Correct. All of these choices are true.
ANSWER: D Ref: Section 7.1
3. The probability density function, f(x), for any continuous random variable X, represents:
A. all possible values that X will assume within some interval a  x  b .
B. the probability that X takes on a specific value x.
C. the height of the density function at x.
D. None of these choices.
Chapter 07
Page 2 of 5
Analysis:
A. Incorrect. It represents the height of the density function at x.
B. Incorrect. It represents the height of the density function at x.
C. Correct. It represents the height of the density function at x.
D. Incorrect. It represents the height of the density function at x.
ANSWER: C Ref: Section 7.1
4. Which of the following is true about f(x) when X has a uniform distribution over the
interval [a, b] ?
A. The values of f(x) are different for various values of the random variable X.
B. f(x) equals one for each possible value of X.
C. f(x) equals one divided by the length of the interval from a to b.
D. None of these choices.
Analysis:
A. Incorrect. f(x) equals one divided by the length of the interval from a to b is true.
B. Incorrect. f(x) equals one divided by the length of the interval from a to b is true.
C. Correct. f(x) equals one divided by the length of the interval from a to b is true.
D. Incorrect. f(x) equals one divided by the length of the interval from a to b is true.
ANSWER: C Ref: Section 7.1
5. Which of the following does not represent a continuous uniform random variable?
A. f(x) = ½ for x between -1 and 1, inclusive.
B. f(x) = 10 for x between 0 and 1/10, inclusive.
C. f(x) = 1/3 for x= 4, 5, 6.
D. None of these choices represents a continuous uniform random variable.
Analysis:
A. Incorrect. f(x) = 1/3 for x= 4, 5, 6 does not represent a continuous uniform random variable.
B. Incorrect. f(x) = 1/3 for x= 4, 5, 6 does not represent a continuous uniform random variable.
C. Correct. f(x) = 1/3 for x= 4, 5, 6 does not represent a continuous uniform random variable.
D. Incorrect. f(x) = 1/3 for x= 4, 5, 6 does not represent a continuous uniform random variable.
ANSWER: C Ref: Section 7.1
6. What is the shape of the probability density function for a uniform random variable on the
interval [a, b]?
A. A rectangle whose X values go from a to b.
B. A straight line whose height is 1/(b-a) over the range [a, b].
C. A continuous probability density function with the same value of f(x) from a to b.
D. All of these choices are true.
Analysis:
A. Incorrect. All of these choices are true.
B. Incorrect. All of these choices are true.
C. Incorrect. All of these choices are true.
D. Correct. All of these choices are true.
ANSWER: D Ref: Section 7.1
Chapter 07
Page 3 of 5
7. A standard normal distribution is a normal distribution with:
A. a mean of zero and a standard deviation of one.
B. a mean of one and a standard deviation of zero.
C. a mean always larger than the standard deviation.
D. None of these choices.
Analysis:
A. Correct. A mean of zero and a standard deviation of one is a standard normal distribution.
B. Incorrect. A mean of zero and a standard deviation of one is a standard normal distribution.
C. Incorrect. A mean of zero and a standard deviation of one is a standard normal distribution.
D. Incorrect. A mean of zero and a standard deviation of one is a standard normal distribution.
ANSWER: A Ref: Section 7.2
8. Given that Z is a standard normal random variable, the area to the left of a value z is
expressed as:
A. P(Z  z)
B. P(Z  z)
C. P(0  Z  z)
D. P(Z  -z)
Analysis:
A. Incorrect. The area to the left of a value z is expressed as P(Z  z).
B. Correct. The area to the left of a value z is expressed as P(Z  z).
C. Incorrect. The area to the left of a value z is expressed as P(Z  z)
D. Incorrect. The area to the left of a value z is expressed as P(Z  z)
ANSWER: B Ref: Section 7.2
9. Which of the following is not a characteristic for a normal distribution?
A. It is symmetrical.
B. The mean is always zero.
C. The mean, median, and mode are all equal.
D. It is a bell-shaped distribution.
ANSWER: b
10. Most values of a standard normal distribution lie between:
A. 0 and 1
B. -3 and 3
C. 0 and 3
D. minus infinity and plus infinity
Analysis:
A. Incorrect. Most values of a standard normal distribution lie between -3 and 3
B. Correct. Most values of a standard normal distribution lie between -3 and 3
C. Incorrect. Most values of a standard normal distribution lie between -3 and 3
D. Incorrect. Most values of a standard normal distribution lie between -3 and 3
ANSWER: B Ref: Section 7.2
Chapter 07
Page 4 of 5
11. Bob took a biology exam whose mean was 70 with standard deviation 5. He also took a
chemistry exam whose mean was 80 with standard deviation 10. He scored 85 on both
exams. On which exam did he do better compared to the other students who took the
exam?
A. He did better on the biology exam, comparatively speaking.
B. He did better on the chemistry exam, comparatively speaking.
C. He did the same on both exams, relatively speaking.
D. Can’t tell without more information.
Analysis:
A. Correct. He did better on the biology exam, comparatively speaking.
B. Incorrect. He did better on the biology exam, comparatively speaking.
C. Incorrect. He did better on the biology exam, comparatively speaking.
D. Incorrect. He did better on the biology exam, comparatively speaking.
ANSWER: A Ref: Section 7.2
12. Which of the following statements is false?
A. The chi-squared distribution is positively skewed.
B. All the values of the chi-squared distribution are non-negative.
C. The shape of the chi-squared distribution depends on its degrees of freedom.
D. All of these choices are true.
Analysis:
A. Incorrect. All of these choices are true.
B. Incorrect. All of these choices are true.
C. Incorrect. All of these choices are true.
D. Correct. All of these choices are true.
ANSWER: D Ref: Section 7.3
13. Which of the following statements is correct regarding the percentile points of the F
distribution?
A. F0.10,10,20  1/ F0.90,10,20
B. F0.10,10,20  1/ F0.10,20,10
C. F0.90,10,20  1/ F0.90,20,10
D. F0.90,10,20  1/ F0.10,20,10
Analysis:
A. Incorrect. The percentile points of the F distribution is F0.90,10,20  1/ F0.10,20,10
B. Incorrect. The percentile points of the F distribution is F0.90,10,20  1/ F0.10,20,10
C. Incorrect. The percentile points of the F distribution is F0.90,10,20  1/ F0.10,20,10
D. Correct. The percentile points of the F distribution is F0.90,10,20  1/ F0.10,20,10
ANSWER: D Ref: Section 7.3
Chapter 07
Page 5 of 5
14. The Student t distribution:
A. is symmetrical.
B. approaches the normal distribution as the degrees of freedom increase.
C. has more area in the tails than the standard normal distribution does.
D. All of these choices are true.
Analysis:
A. Incorrect. All of these choices are true.
B. Incorrect. All of these choices are true.
C. Incorrect. All of these choices are true.
D. Correct. All of these choices are true.
ANSWER: D Ref: Section 7.3
15. Suppose X has a chi-squared distribution with 10 degrees of freedom. The mean of X is:
A. 10
B. 9
C. 20
D. None of these choices.
Analysis:
A. Correct. The mean of X is 10
B. Incorrect. The mean of X is 10
C. Incorrect. The mean of X is 10
D. Incorrect. The mean of X is 10
ANSWER: A Ref: Section 7.3
16. Which of the following distributions is not skewed?
A. Student t
B.  2
C. F
D. All of these distributions are skewed.
Analysis:
A. Correct. Student t is not skewed.
B. Incorrect. Student t is not skewed.
C. Incorrect. Student t is not skewed.
D. Incorrect. Student t is not skewed.
ANSWER: A Ref: Section 7.3