Chapter 7 Test A
Name: __________________________ Date: _____________
1. A survey of 800 women shoppers found that 17% of them shop on impulse. What is the
98% confidence interval for the true proportion of women shoppers who shop on
impulse?
.
 p  0196
.
A) 0144
.
 p  0192
.
B) 0148
.
 p  0.201
C) 0139
.
 p  0.204
D) 0136
2. A sample of 25 different payroll departments found that the employees worked an
average of 310.3 days a year with a standard deviation of 23.8 days. What is the 90%
confidence interval for the average days worked,  , of all payroll departments?
.    319.6
C) 3010
D) 302.4    318.2
A) 298.0    322.6
.    3168
.
B) 3141
3. What is the 90% confidence interval for the variance of exam scores for 28 algebra
students, if the standard deviation of their last exam was 12.7?
C) 10.4   2  16.4
D) 123.7   2  312.7
A) 122.8   2  316.5
B) 108.6   2  269.6
4. A sample of 23 European countries found that the variance on life expectancy was 7.3
years. What is the 95% confidence interval for the variance of life expectancy in
Europe?
A)
4.4    14.6
2
2
B) 27.2    118.3
2
C) 28.9    115.0
2
D) 5.6    10.3
5. Using Table G, find the values for  2 and  2 for  = .05 and n = 22.
left
right
A) 13.091 and 35.172
B) 11.591 and 32.671
C) 12.338 and 33.924
D) 12.7145 and 34.548
6. A researcher conducted a study of the access speed of 45 hard drives and concluded that
his maximum error of estimate was 28. If he were to conduct a second study to reduce
the maximum error of estimate to 7, about how many hard drives should he include in
his new sample?
A) 720
B) 180 C) 45
D) 90
Page 1
Chapter 7 Test A
7. A report states that 42% of home owners had a vegetable garden. How large a sample is
needed to estimate the true proportion of home owners who have vegetable gardens to
within 5% with 98% confidence?
A) 311
B) 528 C) 264
D) 156
8. A study of 80 white mice showed that their average weight was 3.7 ounces. The
standard deviation of the population is 0.6 ounces. Which of the following is the 95%
confidence interval for the mean weight per white mouse?
A) (2.52, 4.88)
B) (3.54, 3.86) C) (3.57, 3.83)
D) (3.39, 4.01)
9. What is the 95% confidence interval for the standard deviation of birth weights at
County General Hospital, if the standard deviation of the last 25 babies born there was
1.1 pounds?
A) 0.7    2.3
B) 0.9    1.5
C) 0.8    2.1
.
D) 0.8    19
10. It was found that in a sample of 90 teenage boys, 70% of them have received speeding
tickets. What is the 90% confidence interval of the true proportion of teenage boys who
have received speeding tickets?
.
 p  0812
.
A) 0591
.
B) 0.615  p  0805
C) 0.620  p  0.780
.
 p  0830
.
D) 0584
11. A recent poll of 700 people who work indoors found that 278 of them smoke. If the
researchers want to be 98% confident of their results to within 3.5%, how large a sample
is necessary?
A) 1062
B) 532
C) 751
D) 1301
12. A previous study of nickels showed that the the standard deviation of the weight of
nickels is 250 milligrams. A coin counter manufacturer wishes to find the 90%
confidence interval for the average weight of a nickel. How many nickels does he need
to weigh to be accurate within 15 milligrams?
A) 457 B) 278 C) 752
D) 1068
Page 2
Chapter 7 Test A
13. 10 squirrels were found to have an average weight of 9.6 ounces with a sample standard
deviation is 0.30. Find the 95% confidence interval of the true mean weight.
A) (8.67, 10.53)
B) (9.36, 9.84)
C) (9.51, 9.69)
D) (9.31, 9.89)
14. In a sample of 855 bartenders, 48% heard complaints from patrons about work. If the
margin of error was 4.4%, what was the confidence level that was used?
A) 99%
B) 90%
C) 95%
D) 98%
15. A random sample of 80 voters found that 44% were going to vote for a certain
candidate. Find the 90% limit for the population proportion of voters who will vote for
that candidate.
A) 39.4% < p < 48.6%
B) 34.9% < p < 53.1%
C) 35.9% < p < 52.1%
D) 36.9% < p < 51.1%
16. The winning team's scores in 7 high school basketball games were recorded. If the
sample mean is 10.3 points and the sample standard deviation is 0.10 points, find the
98% confidence interval of the true mean.
A) (10.18, 10.42)
B) (10.06, 10.54) C) (10.26, 10.34) D) (10.21, 10.39)
17. A previous analysis of paper boxes showed that the the standard deviation of their
lengths is 13 millimeters. A pakcer wishes to find the 80% confidence interval for the
average length of a box. How many boxes does he need to measure to be accurate
within 3 millimeters?
A) 14
B) 19 C) 51
D) 31
18. In a sample of 60 mice, a biologist found that 46% were able to run a maze in 30
seconds or less. Find the 99% limit for the population proportion of mice who can run
that maze in 30 seconds or less.
A) 31.0% < p < 61.0%
B) 21.1% < p < 70.9%
C) 37.7% < p < 54.3%
D) 29.4% < p < 62.6%
Page 3
Chapter 7 Test A
19. A study of 200 apple trees showed that the average number of apples per tree was 1000.
The standard deviation of the population is 200. Which of the following is the 98%
confidence interval for the mean number of apples for all trees?
A) (967.1, 1032.9)
B) (963.8, 1036.2)
C) (963.6, 1036.4)
D) (972.3, 1027.7)
20. In a study of 100 new cars, 31 of them were white. Find p̂ and q̂ where p̂ is the
proportion of new cars that is white.
A) p̂ =0.31, q̂ =0.69
B) p̂ =0.69, q̂ =0.31
C) p̂ =0.69, q̂ =0.69
D) p̂ =0.31, q̂ =0.31
Page 4
Chapter 7 Test A
Answer Key
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2.
3.
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5.
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8.
9.
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11.
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20.
C
D
B
A
B
A
B
C
B
C
A
C
D
A
B
A
D
D
A
A
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