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A. [48.36 50.24]
B. [43.27 55.33]
C. [47.29 51.31]
D. [47.88 50.72]
E. [46.47 52.13] AACSB: Analytic
Bloom's: Application
Difficulty: Hard
Topic: Confidence interval for population mean σ unknown 1675 Chapter 01  An Introduction to Business Statistics 66. An experiment was conducted to determine the effectiveness of a method designed to
remove oil wastes found in soil. Three contaminated soil samples were treated. After 95 days,
the percentage of contamination removed from each soil sample was measured with a mean of
49.3% and a standard deviation of 1.5%. If we wished to narrow the boundary around µ for a
98% confidence interval to within 0.5%, how many soil samples should be in our experiment.
A. 437
B. 33
C. 9
D. 6
E. 3 AACSB: Analytic
Bloom's: Application
Difficulty: Hard
Topic: Sample size determination for population mean 67. A botanist measures the heights of 16 seedlings and obtains a mean and standard deviation
of 72.5 cm and 4.5 cm, respectively. Find the 95% confidence interval for the mean height of
seedlings in the population form which the sample was selected.
A. [62.91 82.09]
B. [70.30 74.70]
C. [70.10 74.90]
D. [70.54 74.46]
E. [71.90 73.10] AACSB: Analytic
Bloom's: Application
Difficulty: Medium
Topic: Confidence interval for population mean σ unknown 1676 Chapter 01  An Introduction to Business Statistics 68. On a standard IQ test, the standard deviation is 15. How many random IQ scores must be
obtained if we want to find the true population mean (with an allowable error of 0.5) and we
want 97% confidence in the results?
A. 4,239
B. 283
C. 212
D. 131
E. 66 AACSB: Analytic
Bloom's: Application
Difficulty: Medium
Topic: Sample size determination for population mean 69. A manufacturer of dodge balls uses a machine to inflate its new balls to a pressure of 13.5
pounds (
= 0.1). When the machine is properly calibrated, the mean inflation pressure s
13.5 pounds, but uncontrollable factors can cause the pressure of individual dodge balls to
vary. For quality control purposes, the manufacturer wishes to estimate the mean inflation
pressure to within 0.025 pounds of its true value with a 99% confidence. What sample size
should be used?
A. 677
B. 107
C. 35
D. 27
E. 11 AACSB: Analytic
Bloom's: Application
Difficulty: Hard
Topic: Confidence interval for population mean σ known 1677 Chapter 01  An Introduction to Business Statistics 70. Recently, a case of food poisoning was traced to a particular restaurant chain. The source
was identified and corrective actions were taken to make sure that the food poisoning would
not reoccur. Despite the response from the restaurant chain, many consumers refused to visit
the restaurant for some time after the event. A survey was conducted three months after the
food poisoning occurred with a sample of 319 patrons contacted. Of the 319 contacted, 29
indicated that they would not go back to the restaurant because of the potential for food
poisoning Construct a 95% confidence interval for the true proportion of the market who still
refuse to visit any of the restaurants in the chain three months after the event.
A. [.059 .122]
B. [.090 .091]
C. [.000 .196]
D. [.240 .339]
E. [.118 .244] AACSB: Analytic
Bloom's: Application
Difficulty: Medium
Topic: Confidence interval for population proportion 71. Recently, a case of food poisoning was traced to a particular restaurant chain. The source
was identified and corrective actions were taken to make sure that the food poisoning would
not reoccur. Despite the response from the restaurant chain, many consumers refused to visit
the restaurant for some time after the event. A survey was conducted three months after the
food poisoning occurred with a sample of 319 patrons contacted. Of the 319 contacted, 29
indicated that they would not go back to the restaurant because of the potential for food
poisoning. What sample size would be needed in order to be 99% confident that the sample
proportion is within .02 of ρ, the true proportion of customers who refuse to go back to the
restaurant?
A. 14
B. 38
C. 129
D. 1,371
E. 1,777 AACSB: Analytic
Bloom's: Application
Difficulty: Medium
Topic: Sample size determination for population proportion 1678 Chapter 01  An Introduction to Business Statistics 72. In a survey of 308 adults, 17% listed jewelry among the romantic gifts men want to
receive. Construct the 98% confidence interval for the proportion of all adults who include
jewelry among their responses.
A. [.025 .085]
B. [.169 .171]
C. [.120 .220]
D. [.140 .200]
E. [.050 .170] AACSB: Analytic
Bloom's: Application
Difficulty: Hard
Topic: Confidence interval for population proportion 73. In a poll of 1,004 adults, 93% indicated that restaurants and bars should refuse service to
patrons who have had too much to drink. Construct the 90% confidence interval for the
proportion of all adults who feel the same way.
A. [.078 .108]
B. [.914 .946]
C. [.920 .940]
D. [.917 .943]
E. [.910 .950] AACSB: Analytic
Bloom's: Application
Difficulty: Hard
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