15, 42, 53, 7, 9, 12, 14, 28, 47
A. 29.1
B. 16.6
C. 17.8
D. 15.8

Exam 4_04
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Part 1 of 1 -
95.0/ 100.0 Points
Question 1 of 20
5.0/ 5.0 Points
The mean score on the exit examination for an urban high school is 63 with a standard deviation
of 9. What is the standard deviation of the distribution of sample means with a sample size of 9?

B. 3
C. 4
D. 4.1
Question 2 of 20
5.0/ 5.0 Points
A final exam in Math 160 has a mean of 73 with standard deviation 7.73. Assume that a random
sample of 24 students is selected and the mean test score of the sample is computed. What
percentage of sample means are less than 70?

Question 3 of 20
0.0/ 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.

Question 4 of 20
5.0/ 5.0 Points

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

Question 5 of 20
5.0/ 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.

Question 6 of 20
5.0/ 5.0 Points
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?

Question 7 of 20
5.0/ 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.

Question 8 of 20
5.0/ 5.0 Points
Decide which of the described variables likely have a normal or near-normal distribution.
a) The amount of change held by a teacher at the end of each day for a year
b) The amount of pocket money held by each student at a mid-sized liberal arts college at a
given time
c) The number of heads that show when two coins are tossed
A. a

B. b
C. c
D. None
Question 9 of 20
5.0/ 5.0 Points
If light bulbs have lives that are normally distributed with a mean of
2500 hours and a standard deviation of 500 hours, what percentage of
light bulbs have a life less than 2500 hours?

Question 10 of 20
5.0/ 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.