52)
A random sample of 110 full–grown lobsters had a mean weight of 16 ounces. Assume that
=3.5 ounces. Construct a 95% confidence interval for the population mean µ.
52)
A)
15.2 to 16.8 ounces
B)
15.4 to 16.6 ounces
C)
15.1 to 16.9 ounces
D)
15.3 to 16.7 ounces
Find the requested value.
53)
A researcher wishes to estimate the mean resting heart rate for long–distance runners. A random
sample of 12 long–distance runners yields the following heart rates, in beats per minute.
79 76 58 72 62 60
79 58 79 68 60 63
Use the data to obtain a point estimate of the mean resting heart rate for all long distance runners.
53)
A)
67.8 beats per minute
B)
64.6 beats per minute
C)
66.2 beats per minute
D)
69.6 beats per minute
Find the requested confidence interval.
54)
A random sample of 30 long distance runners aged 20–25 was selected from a running club. The
resting heart rates (in beats per minute) of the runners are shown below. Estimate the mean resting
heart rate for the population of long distance runners aged 20–25. Assuming = 8.03, give the
95.44% confidence interval for the population mean.
62 70 61 64 75 54 72 68 74 54
75 70 62 66 79 73 81 60 66 76
67 62 66 69 70 86 76 60 53 71
54)
A)
64.10 to 70.10 beats per minute
B)
63.66 to 72.48 beats per minute
C)
65.13 to 71.01 beats per minute
D)
66.60 to 69.54 beats per minute
Solve the problem.
55)
A sample of 75 college students yields a mean annual income of $3041. Assuming that = $833,
find the margin of error in estimating µ at the 99% level of confidence.
55)
A)
$189
B)
$224
C)
$248
D)
$904
Find the requested confidence interval.
56)
A college statistics professor has office hours from 9:00 A.M. to 10:30 A.M. daily. A sample of
waiting times to see the professor (in minutes) is 10, 12, 20, 15, 17, 10, 30, 28, 35, 28, 19, 27, 25, 22, 33,
37, 14, 21, 20, 23. Assuming = 7.84, find the 95.44% confidence interval for the population mean.
56)
A)
–7.7 to 7.8 minutes
B)
19.5 to 35.1 minutes
C)
18.8 to 25.8 minutes
D)
–3.5 to 3.5 minutes
Solve the problem.
57)
Based on a sample of 30 randomly selected years, a 90% confidence interval for the mean annual
precipitation in one city is from 40.3 inches to 43.7 inches. Find the margin of error.
57)
A)
There is not enough information to find the margin of error.
B)
1.7 inches
C)
0.51
D)
3.4 inches
Find the confidence interval specified.
58)
30 students were randomly selected from a large group of students taking a certain calculus test.
The mean score for the students in the sample was 88. Assume that =7.4. Construct a 99%
confidence interval for the mean score, µ, of all students taking the test.
58)
A)
84.67 to 91.33
B)
85.70 to 90.30
C)
84.52 to 91.48
D)
84.53 to 91.47
Provide an appropriate response.
59)
A confidence interval for a population mean has a margin of error of 3.3. If the sample mean is 58.6,
obtain the confidence interval.
59)
A)
From 55.3 to 58.6
B)
From 56.95 to 60.25
C)
From 58.6 to 61.9
D)
From 55.3 to 61.9
60)
Suppose that you wish to obtain a confidence interval for a population mean. Under the conditions
described below, should you use the z–interval procedure, the t–interval procedure, or neither?
– The population standard deviation is unknown.
– The data contain outliers.
– The sample size is small.
60)
A)
Neither
B)
z–interval procedure
C)
t–interval procedure
Solve the problem.
61)
A confidence interval for a population mean, µ, has length 12. Find the margin of error.
61)
A)
36
B)
3
C)
12
D)
6
Provide an appropriate response.
62)
Which of the following statements regarding t–curves is/are true?
A. The total area under a t–curve with 10 degrees of freedom is greater than the area under the
standard normal curve.
B. The t–curve with 10 degrees of freedom is flatter and wider than the standard normal curve.
C. The t–curve with 10 degrees of freedom more closely resembles the standard normal curve than
the t–curve with 20 degrees of freedom.
62)
A)
A
B)
B, C
C)
B
D)
C
Find the specified t–value.
63)
For a t–curve with df = 9, find the t–value having area 0.005 to its left.
63)
A)
1.833
B)
3.250
C)
–3.250
D)
–1.833
Find the requested confidence interval.
64)
A college statistics professor has office hours from 9:00 A.M. to 10:30 A.M. daily. A sample of
waiting times to see the professor (in minutes) is 10, 12, 20, 15, 17, 10, 30, 28, 35, 28, 19, 27, 25, 22, 33,
37, 14, 21, 20, 23. Assuming = 7.84, find the 99.74% confidence interval for the population mean.
64)
A)
19.5 to 35.1 minutes
B)
18.8 to 25.8 minutes
C)
20.55 to 24.05 minutes
D)
17.05 to 27.55 minutes
Solve the problem.
65)
A sample of 93 women aged 18–24 yields a mean systolic blood pressure of114.2 mm Hg.
Assuming that =13.0 mm Hg, find the margin of error in estimating µ at the 95% level of
confidence.
65)
A)
50.6 mm Hg
B)
2.6 mm Hg
C)
2.4 mm Hg
D)
2.1 mm Hg
Find the confidence interval specified. Assume that the population is normally distributed.
66)
A savings and loan association needs information concerning the checking account balances of its
local customers. A random sample of 14 accounts was checked and yielded a mean balance of
$664.14 and a standard deviation of $297.29. Find a 90% confidence interval for the true mean
checking account balance for local customers.
66)
A)
$523.43 to $804.85
B)
$493.71 to $834.57
C)
$455.65 to $872.63
D)
$492.52 to $835.76
Provide an appropriate response.
67)
Suppose that scores for men on an aptitude test have greater variability than scores for women on
the same test. In other words, the population standard deviation is greater for the population of
men than for the population of women. Based on a sample of size 50, a 95% confidence interval for
the mean score, µ, of all women has a margin of error of 2.2. Which of the following confidence
intervals will have a smaller margin of error?
A. A 99% confidence interval for the mean score of women. Sample size = 50
B. A 95% confidence interval for the mean score of women. Sample size = 100
C. A 95% confidence interval for the mean score of men. Sample size = 50
67)
A)
A, B, C
B)
C
C)
A
D)
B
Find the specified t–value.
68)
For a t–curve with df = 23, find the t–value having area 0.10 to its left.
68)
A)
2.500
B)
1.319
C)
–2.500
D)
–1.319
Solve the problem.
69)
Based on a sample of size 42, a 95% confidence interval for the mean score of all students, µ, on an
aptitude test is from 57.1 to 64.9. Find the margin of error.
69)
A)
7.8
B)
3.9
C)
There is not enough information to find the margin of error.
D)
1.18
Find the confidence interval specified.
70)
Physiologists often use the forced vital capacity as a way to assess a person‘s ability to move air in
and out of their lungs. A researcher wishes to estimate the forced vital capacity of people suffering
from asthma. A random sample of 15 asthmatics yields the following data on forced vital capacity,
in liters.
4.6 2.9 3.7 3.0 4.9
3.7 3.7 4.3 3.5 5.2
3.2 3.5 4.8 4.0 5.1
Use the data to obtain a 95.44% confidence interval for the mean forced vital capacity for all
asthmatics. Assume that =0.8.
70)
A)
59.69 to 60.51 liters
B)
2.41 to 5.61 liters
C)
3.59 to 4.42 liters
D)
3.90 to 4.11 liters
Provide an appropriate response.
71)
Find the confidence level that corresponds to a value of of 0.05.
71)
A)
0.025%
B)
0.95%
C)
95%
D)
5%
72)
Suppose that you wish to obtain a confidence interval for a population mean. Under the conditions
described below, should you use the z–interval procedure, the t–interval procedure, or neither?
– The population standard deviation is known.
– The population is not normally distributed.
– The sample size is 12.
72)
A)
t–interval procedure
B)
z–interval procedure
C)
Neither
73)
Give an expression for the confidence level in terms of .
73)
A)
1 –%
B)
1 –
100%
C)
100(1 –)%
D)
100%
74)
Find the value of that corresponds to a confidence level of 96%.
74)
A)
4
B)
0.004
C)
0.04
D)
0.96
Solve the problem.
75)
A sample of 40 washing machines yields a mean replacement time of 11.5 years. Assuming that
=2.4 years, find the margin of error in estimating µ at the 90% level of confidence.
75)
A)
3.0 years
B)
0.1 years
C)
0.5 years
D)
0.6 years
Find the confidence interval specified. Assume that the population is normally distributed.
76)
A sociologist develops a test to measure attitudes about public transportation, and 27 randomly
selected subjects are given the test. Their mean score is 76.2 and their standard deviation is 21.4.
Construct the 95% confidence interval for the mean score of all such subjects.
76)
A)
67.7 to 84.7
B)
69.2 to 83.2
C)
64.2 to 88.2
D)
74.6 to 77.8
77)
Thirty randomly selected students took the calculus final. If the sample mean was 92 and the
standard deviation was 8.8, construct a 99% confidence interval for the mean score of all students.
77)
A)
87.57 to 96.43
B)
89.27 to 94.73
C)
87.59 to 96.41
D)
88.04 to 95.96
78)
A random sample of 30 households was selected from a particular neighborhood. The number of
cars for each household is shown below. Estimate the mean number of cars per household for the
population of households in this neighborhood. Give the 95% confidence interval.
2 0 1 2 3 2 1 0 1 4
1 3 2 0 1 1 2 3 1 2
1 0 3 2 0 2 2 1 0 2
78)
A)
1 to 2 cars
B)
1.1 to 1.9 cars
C)
1.5 to 1.9 cars
D)
1.3 to 1.7 cars
Find the necessary sample size.
79)
The monthly earnings of a group of business students are are normally distributed with a standard
deviation of 589 dollars. A researcher wants to estimate the mean monthly earnings of all business
students. Find the sample size needed to have a confidence level of 95% and a margin of error of
132 dollars.
79)
A)
4
B)
67
C)
77
D)
2
Find the specified t–value.
80)
For a t–curve with df = 18, find the t–value having area 0.05 to its right.
80)
A)
2.878
B)
2.101
C)
1.740
D)
1.734
Solve the problem.
81)
A confidence interval for a population mean, µ, has length 104.6. Find the margin of error.
81)
A)
104.6
B)
209.2
C)
52.3
D)
10,941.16
Find the confidence interval specified.
82)
A random sample of 93 light bulbs had a mean life of x=546 hours. Assume that =26 hours.
Construct a 90% confidence interval for the mean life, µ, of all light bulbs of this type.
82)
A)
539.7 to 552.3 hours
B)
541.6 to 550.4 hours
C)
539.0 to 553.0 hours
D)
540.7 to 551.3 hours
83)
The mean score, x, on an aptitude test for a random sample of 3 students was 71. Assuming that
=13, construct a 95.44% confidence interval for the mean score, µ, of all students taking the test.
83)
A)
59.7 to 82.3
B)
56.0 to 86.0
C)
62.3 to 79.7
D)
45 to 97
Find the requested confidence interval.
84)
The data below consists of the pulse rates (in beats per minute) of 32 students. Assuming = 10.66,
obtain a 95.44% confidence interval for the population mean.
80 74 61 93 69 74 80 64
51 60 66 87 72 77 84 96
60 67 71 79 89 75 66 70
57 76 71 92 73 72 68 74
84)
A)
69.62 to 77.14 beats per minute
B)
70.65 to 76.27 beats per minute
C)
68.55 to 78.23 beats per minute
D)
51.53 to 95.26 beats per minute
Answer Key
Testname: C8
23
Answer Key
Testname: C8
Answer Key
Testname: C8