Question 1

A study of a company's practice regarding the payment of invoices revealed that on the average an
Invoice was paid 20 days after it was received. The standard deviation equalled ﬁve days.
Assuming that the distribution is normal, what percent of the invoices were paid within 15 days of
Receipt?

Accepted Answer

A)   15.87%
B)   37.91%
C)   34.13%
D)   86.74%E) None of the above
F) B) and C)

Question 2

Which of the following is NOT a characteristic of the normal probability distribution?

Accepted Answer

A)   Positively-skewed
B)   Bell-shaped
C)   Symmetrical
D)   AsymptoticE) B) and C)
F) All of the above

Question 3

The mean of a normally distributed group of weekly incomes of a large group of executives is
$1,000 and the standard deviation is $100. What is the z-score for an income of $1,100?

Accepted Answer

A)   1.00
B)   2.00
C)   1.683
D)   - 0.90E) None of the above
F) All of the above

Question 4

An accelerated life test on a large number of type-D alkaline batteries revealed that the mean life
For a particular use before they failed is 19.0 hours. The distribution of the lives approximated a
Normal distribution. The standard deviation of the distribution was 1.2 hours. About 95.44 percent of
The batteries failed between what two values?

Accepted Answer

A)   8.9 and 18.9
B)   12.2 and 14.2
C)   14.1 and 22.1
D)   16.6 and 21.4E) A) and B)
F) A) and D)

Question 5

Determine the z-score associated with an area of 0.4925 from the mean of a normal distribution to
That negative z-score.

Accepted Answer

A)   2.43
B)   -2.43
C)   -2.4
D)   2.4
E)   -2.44F) B) and E)
G) C) and E)

Question 6

The seasonal output of a new experimental strain of pepper plants was carefully weighed. The
Mean weight per plant is 15.0 pounds, and the standard deviation of the normally distributed
Weights is 1.75 pounds. Of the 200 plants in the experiment, how many produced peppers weighing
Between 13 and 16 pounds?

Accepted Answer

A)   100
B)   118
C)   197
D)   53E) A) and B)
F) A) and D)

Question 7

A loaf of bread is normally distributed with a mean of 22 ounces and a standard deviation of ½
Ounces.
(i. The probability that a loaf of bread is between 20.75 and 23.25 ounces is 0.9876.
(ii. The probability that a loaf of bread is > 21 ounces is 0.9772.

Accepted Answer

A)   (i)  and (ii)  are correct statements.
B)   (i)  is a correct statement but not (ii) .
C)   (ii)  is a correct statement but not (i) .
D)   (i)  and (i)  are false statements.E) A) and B)
F) None of the above

Question 8

The upper and lower limits of a uniform probability distribution are

Accepted Answer

A)   positive and negative inﬁnity.
B)   plus and minus three standard deviations.
C)   0 and 1.
D)   the maximum and minimum values of the random variable.E) A) and B)
F) B) and C)

Question 9

The average score of 100 students taking a statistics ﬁnal was 70 with a standard deviation of 7.
Assuming a normal distribution, approximately how many scored greater than 65?

Accepted Answer

A)   0.2611
B)   0.2389
C)   0.7611
D)   
D)  -0.714E) A) and B)
F) A) and C)

Question 10

A sample of 500 evening students revealed that their annual incomes were normally distributed
With a mean income of $50,000 and a standard deviation of $4,000. What is the income that
Separates the top 5% from the lower 95% of the incomes?

Accepted Answer

A)   $43,420
B)   $47,320
C)   $56,580
D)   $52,680E) A) and B)
F) None of the above

Question 11

i. A z-score is the distance between a selected value (X)  and the population mean (μ)  divided by the
Population standard deviation (σ) .
ii. The standard normal distribution is a special normal distribution with a mean of 0 and a standard
Deviation of 1.
iii. A computed z for X values to the right of the mean is negative.

Accepted Answer

A)   (i) , (ii) , and (iii)  are all correct statements.
B)   (i)  is a correct statement but not (ii)  or (iii) .
C)   (i)  and (iii)  are correct statements but not (ii) .
D)   (i)  and (ii)  are correct statements but not (iii) .
E)   (i) , (ii) , and (iii)  are all false statements.F) B) and E)
G) A) and B)

Question 12

The mean amount of gasoline and services charged by Key Reﬁning Company credit customers is
$70 per month. The distribution of amounts spent is approximately normal with a standard deviation
Of $10. What is the probability of selecting a credit card customer at random and ﬁnding the
Customer charged between $70 and $83?

Accepted Answer

A)   0.1962
B)   0.4032
C)   0.3413
D)   0.4750E) B) and C)
F) A) and C)

Question 13

Past experience of a large manufacturing ﬁrm with administering a test to recent college graduates
Who had applied for a job revealed that the mean test score was 500, and the standard deviation
Was 50. The distribution of the test scores was normal. Based on this experience, management is
Considering placing a person whose score is in the upper 6 percent of the distribution directly into a
Responsible position. What is the lowest score a college graduate must earn to qualify for a
Responsible position?

Accepted Answer

A)   50
B)   625
C)   460
D)   578E) A) and B)
F) C) and D)

Question 14

Determine the z-score associated with an area of .1950 from the mean of a normal distribution to
That positive z-score.

Accepted Answer

A)   0.41
B)   0.51
C)   0.5
D)   0.01
E)   -0.41F) B) and D)
G) A) and B)

Question 15

(i. About 95.5% percent of the area under the normal curve is within plus three and minus three
Standard deviations of the mean.
(ii. The normal distribution is a continuous probability distribution.
(iii)  In a standard normal distribution, µ = 0 and σ = 1.

Accepted Answer

A)   (i) , (ii) , and (iii)  are all correct statements.
B)   (i)  is a correct statement but not (ii)  or (iii) .
C)   (i)  and (iii)  are correct statements but not (ii) .
D)   (i)  and (ii)  are correct statements but not (iii) .
E)   (ii)  and (iii)  are correct statements but not (i) .F) D) and E)
G) B) and E)

Question 16

From past history, the scores on a statistics test are normally distributed with a mean of 70% and a
Standard deviation of 5%. To earn a "C" on the test, a student must be in the top 25% of the class.
What should a student score to receive a "C"?

Accepted Answer

A)   77.21
B)   73.37
C)   73.96
D)   76.90E) A) and B)
F) B) and C)

Question 17

Two competitive brothers, who work in two different industries, were comparing their salaries.
Because there is a difference of 4 years in their respective work experience, they decided to
Compare, not their actual salaries, but to compare their salaries against their company averages to
See who is doing better. The following gives the brothers salaries, companies mean, and standard
Deviation for each company. 
What is the z-score of Andy's salary?

Accepted Answer

A)   - 1.29
B)   1.29
C)   - 1.89
D)   1.89E) A) and D)
F) B) and C)

Question 18

The average score of 100 students taking a statistics ﬁnal was 70 with a standard deviation of 7.
Assuming a normal distribution, approximately how many scored less than 60?

Accepted Answer

A)   0.2271
B)   0.3729
C)   0.8929
D)   
D)  -1.14
E)   0.0764F) D) and E)
G) A) and C)

Question 19

i. The mean of a normal distribution is represented by σ.
ii. When referring to the normal probability function, there is not just one of them; there is a "family"
Of them.
iii. Some normal probability distributions have equal arithmetic means, but their standard deviations
May be different.

Accepted Answer

A)   (i) , (ii) , and (iii)  are all correct statements.
B)   (i)  is a correct statement but not (ii)  or (iii) .
C)   (i)  and (iii)  are correct statements but not (ii) .
D)   (ii)  and (iii)  are correct statements but not (i) .
E)   (i) , (ii) , and (iii)  are all false statements.F) A) and B)
G) C) and D)

Question 20

A loaf of bread is normally distributed with a mean of 22 ounces and a standard deviation of ½
Ounces.
(i. The probability that a loaf of bread is  21 ounces is 0.9772.
(iii)  The probability that a loaf of bread is < 24 ounces is 0.00.

Accepted Answer

A)   (i) , (ii) , and (iii)  are all correct statements.
B)   (i)  is a correct statement but not (ii)  or (iii) .
C)   (i)  and (iii)  are correct statements but not (ii) .
D)   (i)  and (ii)  are correct statements but not (iii) .
E)   (ii)  and (iii)  are correct statements but not (i) .F) A) and B)
G) C) and D)

Exam 6: Discrete Probability Distributions

Correct Answer
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The upper and lower limits of a uniform probability distribution are

Correct Answer
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i. The mean of a normal distribution is represented by σ. ii. When referring to the normal probability function, there is not just one of them; there is a "family" Of them. iii. Some normal probability distributions have equal arithmetic means, but their standard deviations May be different.

Correct Answer
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Correct Answer
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The average score of 100 students taking a statistics ﬁnal was 70 with a standard deviation of 7. Assuming a normal distribution, approximately how many scored greater than 65?

Correct Answer
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Correct Answer
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Correct Answer
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A sample of 500 evening students revealed that their annual incomes were normally distributed With a mean income of $50,000 and a standard deviation of $4,000. What is the income that Separates the top 5% from the lower 95% of the incomes?

Correct Answer
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Determine the z-score associated with an area of .1950 from the mean of a normal distribution to That positive z-score.

Correct Answer
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Which of the following is NOT a characteristic of the normal probability distribution?

Correct Answer
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A loaf of bread is normally distributed with a mean of 22 ounces and a standard deviation of ½ Ounces. (i. The probability that a loaf of bread is between 20.75 and 23.25 ounces is 0.9876. (ii. The probability that a loaf of bread is > 21 ounces is 0.9772.

Correct Answer
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Correct Answer
verified

(i. About 95.5% percent of the area under the normal curve is within plus three and minus three Standard deviations of the mean. (ii. The normal distribution is a continuous probability distribution. (iii) In a standard normal distribution, µ = 0 and σ = 1.

Correct Answer
verified

The mean of a normally distributed group of weekly incomes of a large group of executives is $1,000 and the standard deviation is $100. What is the z-score for an income of $1,100?

Correct Answer
verified

Determine the z-score associated with an area of 0.4925 from the mean of a normal distribution to That negative z-score.

Correct Answer
verified

A study of a company's practice regarding the payment of invoices revealed that on the average an Invoice was paid 20 days after it was received. The standard deviation equalled ﬁve days. Assuming that the distribution is normal, what percent of the invoices were paid within 15 days of Receipt?

Correct Answer
verified

Correct Answer
verified

From past history, the scores on a statistics test are normally distributed with a mean of 70% and a Standard deviation of 5%. To earn a "C" on the test, a student must be in the top 25% of the class. What should a student score to receive a "C"?

Correct Answer
verified

Correct Answer
verified

The average score of 100 students taking a statistics ﬁnal was 70 with a standard deviation of 7. Assuming a normal distribution, approximately how many scored less than 60?

Correct Answer
verified

Exam 6: Discrete Probability Distributions

Correct AnswerverifiedShow Answer

The upper and lower limits of a uniform probability distribution are

Correct AnswerverifiedShow Answer

i. The mean of a normal distribution is represented by σ. ii. When referring to the normal probability function, there is not just one of them; there is a "family" Of them. iii. Some normal probability distributions have equal arithmetic means, but their standard deviations May be different.

Correct AnswerverifiedShow Answer

Correct AnswerverifiedShow Answer

The average score of 100 students taking a statistics ﬁnal was 70 with a standard deviation of 7. Assuming a normal distribution, approximately how many scored greater than 65?

Correct AnswerverifiedShow Answer

Correct AnswerverifiedShow Answer

Correct AnswerverifiedShow Answer

A sample of 500 evening students revealed that their annual incomes were normally distributed With a mean income of $50,000 and a standard deviation of $4,000. What is the income that Separates the top 5% from the lower 95% of the incomes?

Correct AnswerverifiedShow Answer

Determine the z-score associated with an area of .1950 from the mean of a normal distribution to That positive z-score.

Correct AnswerverifiedShow Answer

Which of the following is NOT a characteristic of the normal probability distribution?

Correct AnswerverifiedShow Answer

A loaf of bread is normally distributed with a mean of 22 ounces and a standard deviation of ½ Ounces. (i. The probability that a loaf of bread is between 20.75 and 23.25 ounces is 0.9876. (ii. The probability that a loaf of bread is > 21 ounces is 0.9772.

Correct AnswerverifiedShow Answer

Correct AnswerverifiedShow Answer

(i. About 95.5% percent of the area under the normal curve is within plus three and minus three Standard deviations of the mean. (ii. The normal distribution is a continuous probability distribution. (iii) In a standard normal distribution, µ = 0 and σ = 1.

Correct AnswerverifiedShow Answer

The mean of a normally distributed group of weekly incomes of a large group of executives is $1,000 and the standard deviation is $100. What is the z-score for an income of $1,100?

Correct AnswerverifiedShow Answer

Determine the z-score associated with an area of 0.4925 from the mean of a normal distribution to That negative z-score.

Correct AnswerverifiedShow Answer

A study of a company's practice regarding the payment of invoices revealed that on the average an Invoice was paid 20 days after it was received. The standard deviation equalled ﬁve days. Assuming that the distribution is normal, what percent of the invoices were paid within 15 days of Receipt?

Correct AnswerverifiedShow Answer

Correct AnswerverifiedShow Answer

From past history, the scores on a statistics test are normally distributed with a mean of 70% and a Standard deviation of 5%. To earn a "C" on the test, a student must be in the top 25% of the class. What should a student score to receive a "C"?

Correct AnswerverifiedShow Answer

Correct AnswerverifiedShow Answer

The average score of 100 students taking a statistics ﬁnal was 70 with a standard deviation of 7. Assuming a normal distribution, approximately how many scored less than 60?

Correct AnswerverifiedShow Answer

Correct Answer
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Correct Answer
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Correct Answer
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