BUSINESS STATS CH. 9 TEST BANK
EXAM 2025/2026 QUESTIONS AND
ANSWERS 100% PASS
The mean number of travel days per year for salespeople employed by three hardware
distributors needs to be estimated with a 0.90 degree of confidence. For a small pilot study, the
mean was 150 days and the standard deviation was 14 days. If the population mean is
estimated within two days, how many salespeople should be sampled? - ANS 133
A research firm needs to estimate within 3% the proportion of junior executives leaving large
manufacturing companies within three years. A 0.95 degree of confidence is to be used. Several
years ago, a study revealed that 21% of junior executives left their company within three years.
To update this study, how many junior executives should be surveyed? - ANS 709
There are 2,000 eligible voters in a precinct. A total of 500 voters are randomly selected and
asked whether they plan to vote for the Democratic incumbent or the Republican challenger. Of
the 500 surveyed, 350 said they would vote for the Democratic incumbent. Using the 0.99
confidence coefficient, what are the confidence limits for the proportion that plan to vote for
the Democratic incumbent? - ANS 0.647 and 0.753
A random sample of 85 supervisors revealed that they worked an average of 6.5 years before
being promoted. The population standard deviation was 1.7 years. Using the 0.95 degree of
confidence, what is the confidence interval for the population mean? - ANS 6.14 and 6.86
1 @COPYRIGHT 2025/2026 ALLRIGHTS RESERVED.
, The mean weight of trucks traveling on a particular section of I-475 is not known. A state
highway inspector needs an estimate of the population mean. He selects and weighs a random
sample of 49 trucks and finds the mean weight is 15.8 tons. The population standard deviation
is 3.8 tons. What is the 95% confidence interval for the population mean? - ANS 14.7 and
16.9
A bank wishes to estimate the mean credit card balance owed by its customers. The population
standard deviation is estimated to be $300. If a 98% confidence interval is used and an interval
of $75 is desired, how many customers should be sampled? - ANS 87
Mileage tests were conducted on a randomly selected sample of 100 newly developed
automobile tires. The results showed that the mean tread life was 50,000 miles, with a standard
deviation of 3,500 miles. What is the best estimate of the mean tread life in miles for the entire
population of these tires? - ANS 50,000
What is the interpretation of a 96% confidence level? - ANS Approximately 96 out of 100
such intervals would include the true value of the population parameter.
Which statement(s) is/are correct about the t distribution? - ANS All apply
What kind of distribution is the t distribution? - ANS Continuous
How is the t distribution similar to the standard z distribution? - ANS Both are continuous
distributions.
A random sample of 20 items is selected from a population. When computing a confidence
interval for the population mean, what number of degrees of freedom should be used to
determine the appropriate t-value? - ANS 19
2 @COPYRIGHT 2025/2026 ALLRIGHTS RESERVED.
EXAM 2025/2026 QUESTIONS AND
ANSWERS 100% PASS
The mean number of travel days per year for salespeople employed by three hardware
distributors needs to be estimated with a 0.90 degree of confidence. For a small pilot study, the
mean was 150 days and the standard deviation was 14 days. If the population mean is
estimated within two days, how many salespeople should be sampled? - ANS 133
A research firm needs to estimate within 3% the proportion of junior executives leaving large
manufacturing companies within three years. A 0.95 degree of confidence is to be used. Several
years ago, a study revealed that 21% of junior executives left their company within three years.
To update this study, how many junior executives should be surveyed? - ANS 709
There are 2,000 eligible voters in a precinct. A total of 500 voters are randomly selected and
asked whether they plan to vote for the Democratic incumbent or the Republican challenger. Of
the 500 surveyed, 350 said they would vote for the Democratic incumbent. Using the 0.99
confidence coefficient, what are the confidence limits for the proportion that plan to vote for
the Democratic incumbent? - ANS 0.647 and 0.753
A random sample of 85 supervisors revealed that they worked an average of 6.5 years before
being promoted. The population standard deviation was 1.7 years. Using the 0.95 degree of
confidence, what is the confidence interval for the population mean? - ANS 6.14 and 6.86
1 @COPYRIGHT 2025/2026 ALLRIGHTS RESERVED.
, The mean weight of trucks traveling on a particular section of I-475 is not known. A state
highway inspector needs an estimate of the population mean. He selects and weighs a random
sample of 49 trucks and finds the mean weight is 15.8 tons. The population standard deviation
is 3.8 tons. What is the 95% confidence interval for the population mean? - ANS 14.7 and
16.9
A bank wishes to estimate the mean credit card balance owed by its customers. The population
standard deviation is estimated to be $300. If a 98% confidence interval is used and an interval
of $75 is desired, how many customers should be sampled? - ANS 87
Mileage tests were conducted on a randomly selected sample of 100 newly developed
automobile tires. The results showed that the mean tread life was 50,000 miles, with a standard
deviation of 3,500 miles. What is the best estimate of the mean tread life in miles for the entire
population of these tires? - ANS 50,000
What is the interpretation of a 96% confidence level? - ANS Approximately 96 out of 100
such intervals would include the true value of the population parameter.
Which statement(s) is/are correct about the t distribution? - ANS All apply
What kind of distribution is the t distribution? - ANS Continuous
How is the t distribution similar to the standard z distribution? - ANS Both are continuous
distributions.
A random sample of 20 items is selected from a population. When computing a confidence
interval for the population mean, what number of degrees of freedom should be used to
determine the appropriate t-value? - ANS 19
2 @COPYRIGHT 2025/2026 ALLRIGHTS RESERVED.
