Statistics-At one college, GPA’s are normally distributed with a mean of 2.9

5.0 Points
Question 1 of 20
At one college, GPA’s are normally distributed with a mean of 2.9 and a standard deviation of 0.6. Find the 70th
percentile.

A. 3.53

B. 3.42

C. 3.23

D. 3.13
5.0 Points
Question 2 of 20
The scores on a certain test are normally distributed with a mean score of 58 and a standard deviation of 4. What is
the likelihood that a sample of 90 students will have a mean score of at least 58.4216?

A. 0.8413

B. 0.3413

C. 0.3174

D. 0.1587
Decide which of the described variables is/are likely to have a normal or near-normal distribution.
a) The heights of corn stalks in one row of corn that is half a mile long
b) The numbers of viewers of each of the channels from 202 to 550 on Direct TV at 7:00 PM CDT on the third
Thursday of November 2012 (349 data values)

A. a

B. b

C. a and b

D. neither
Decide which of the described variables likely have a normal or near-normal distribution.
1. The number of credits remaining until graduation for the students in a small liberal arts college
2. The heights of male students in an advanced placement mathematics class
3. The number of sixes showing when two dice are rolled

A. a

B. b

C. c

D. None
5.0 Points
Question 5 of 20
If light bulbs have lives that are normally distributed with a mean of 2500 hours and a standard deviation of 500
hours, use the 68-95-99.7 rule to approximate the percentage of light bulbs having a life between 2000 hours and
3500 hours?

A. About 13.5%

B. About 50%

C. About 68%

D. About 81.5%
5.0 Points
Question 6 of 20
The mean score on the exit examination for an urban high school is 63 with a standard deviation of 8. What is the
mean of the distribution of sample means with a sample size of 9?

A. 62

B. 63

C. 63.5

D. 64
Question 7 of 20

5.0 Points

The area under the standard normal curve between 1 and 2 is equal to 0.1359. Scores on a particular aptitude test
are normally distributed with a mean of 100 and a standard deviation of 10. Which of the following are equal to
13.59%?
a) The percentage of scores between 120 and 130
b) The percentage of scores between 110 and 120
c) The percentage of scores between 80 and 90
d) The percentage of scores between 90 and 120

A. b

B. b, c

C. d

D. a, b
5.0 Points
Question 9 of 20
The volumes of soda in quart soda bottles are normally distributed with a mean of 32.3 oz and a standard deviation of
1.2 oz. What is the probability that the volume of soda in a randomly selected bottle will be less than 32 oz?

A. 0.5012

B. 0.5010

C. 0.4015

D. 0.4013
Question 10 of 20

5.0 Points

The lifetimes of projector bulbs of a particular type are normally distributed with a mean of 470 hours and a standard
deviation of 15 hours. What percentage of the bulbs has lifetimes that lie within 2 standard deviations of the mean on
either side?
Apply the 68-95-99.7 rule to this question.

A. 68%

B. 99.7%

C. 95%

D. 100%
Question 11 of 20

5.0 Points

The lifetimes of light bulbs of a particular type are normally distributed with a mean of 270 hours and a standard
deviation of 11 hours. What percentage of the bulbs has lifetimes that lie within 2 standard deviations of the mean on
either side?
Apply the 68-95-99.7 rule to this questions.

A. 68%

B. 1005

C. 99.7%

D. 95%
5.0 Points
Question 12 of 20
The systolic blood pressures of the patients at a hospital are normally distributed with a mean of 136 mm Hg and a
standard deviation of 12 mm Hg. Find the two blood pressures having these properties: the mean is midway between
them and 76.98% of all blood pressures are between them.

A. 121.6, 152.4

B. 121.6, 150.4

C. 123.6, 150.4

D. 122.6, 148.4
5.0 Points
Question 13 of 20
A bank’s loan officer rates applicants for credit. The ratings are normally distributed with a mean of 200 and a
standard deviation of 50. If an applicant is randomly selected, find the probability of a rating that is between 225 and
275.

A. 0.2416

B. 0.2418

C. 0.2417

D. 0.2420
Question 14 of 20

5.0 Points

The systolic blood pressure of 18-year-old women is normally distributed with a mean of 120 mm Hg and a standard
deviation of 12 mm Hg. What percentage of 18-year-old women have a systolic blood pressure that is within 3
standard deviations of the mean on either side?
Apply the 68-95-99.7 rule to this question.

A. 68%

B. 95%

C. 100%

D. 99.7%
5.0 Points
Question 15 of 20
The diameters of pencils produced by a certain machine are normally distributed with a mean of 0.30 inches and a
standard deviation of 0.01 inches. In a random sample of 460 pencils, approximately how many would you expect to
have a diameter less than 0.293 inches?

A. 123

B. 118

C. 112

D. 111
5.0 Points
Question 16 of 20
The diameters of bolts produced by a certain machine are normally distributed with a mean of 0.25 inches and a
standard deviation of 0.01 inches. What percentage of bolts will have a diameter greater than 0.24 inches?

A. 79.13%

B. 82.46%

C. 84.13%

D. 84.46%
Question 17 of 20

5.0 Points

Which of the following statements concerning the standard normal curve is/are true (if any)?
a) The area under the standard normal curve to the left of -3 is zero.
b) The area under the standard normal curve between any two z-scores is greater than zero.
c) The area under the standard normal curve between two z-scores will be negative if both z-scores are negative.
d) The area under the standard normal curve to the left of any z-score is less than 1.

A. a, b

B. b, d

C. a, c

D. a

Question 18 of 20

5.0 Points

The annual precipitation for one city is normally distributed with a mean of 72 inches and a standard deviation of 3.5
inches. Fill in the blanks.
In 99.7% of the years, the precipitation in this city is between __________ and __________ inches.
Apply the 68-95-99.7 rule to this questions.

A. 61.5, 82. 5

B. 82.5, 61.5

C. 61.5, 85.5

D. 63.5, 82.5
Question 19 of 20

5.0 Points

The amount of Jen’s monthly electric bill is normally distributed with a mean of $160 and a standard deviation of $14.
Fill in the blanks.
95% of her electric bills are between __________ and __________.
Apply the 68-95-99.7 rule to this question.

A. $140, $190

B. $132, $190

C. $140, $188

D. $132, $188
Question 20 of 20

5.0 Points

The annual precipitation for one city is normally distributed with a mean of 28 inches and a standard deviation of 3.4
inches. Fill in the blanks.
In 95% of the years, the precipitation in this city is between __________ and __________ inches.

Apply the 68-95-99.7 rule to this question.

A. 21.2, 34.8

B. 21.2, 34.6

C. 22.4, 34.6

D. 22.4, 34.8