TEST BANK for Business and Society 17th Edition by
Lawrence & Weber
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? - ANSWER: 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? - ANSWER: 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?
- ANSWER: 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? - ANSWER: 6.14 and 6.86
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? - ANSWER: 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? -
ANSWER: 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? - ANSWER: 50,000
, What is the interpretation of a 96% confidence level? - ANSWER: 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? - ANSWER: All apply
What kind of distribution is the t distribution? - ANSWER: Continuous
How is the t distribution similar to the standard z distribution? - ANSWER: 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? - ANSWER: 19
Of the following characteristics, the t distribution and z distribution are the same in
all BUT one. Which one is it? - ANSWER: Mean = 0, and standard deviation = 1
Suppose 1,600 of 2,000 registered voters sampled said they planned to vote for the
Republican candidate for president. Using the 0.95 degree of confidence, what is the
interval estimate for the population proportion (to the nearest 10th of a percent)? -
ANSWER: 78.2% to 81.8%
Which of the following is NOT necessary to determine how large a sample to select
from a population? - ANSWER: The size of the population
A sample mean is the best point estimate of _______. - ANSWER: the population
mean
A sample standard deviation is the best point estimate of the ___________. -
ANSWER: population standard deviation
A confidence interval for a population mean __________. - ANSWER: estimates a
likely interval for a population mean
Knowing the population standard deviation, a 95% confidence interval infers that the
population mean ___________. - ANSWER: is within ±1.96 standard errors of the
sample mean
When a confidence interval for a population mean is constructed from sample data,
__________. - ANSWER: we can conclude, for an infinite number of samples and
corresponding confidence intervals, that the population mean is in a stated
percentage of the intervals
The distribution of Student's t has _________. - ANSWER: a mean of zero and a
standard deviation that depends on the sample size
Lawrence & Weber
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? - ANSWER: 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? - ANSWER: 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?
- ANSWER: 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? - ANSWER: 6.14 and 6.86
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? - ANSWER: 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? -
ANSWER: 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? - ANSWER: 50,000
, What is the interpretation of a 96% confidence level? - ANSWER: 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? - ANSWER: All apply
What kind of distribution is the t distribution? - ANSWER: Continuous
How is the t distribution similar to the standard z distribution? - ANSWER: 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? - ANSWER: 19
Of the following characteristics, the t distribution and z distribution are the same in
all BUT one. Which one is it? - ANSWER: Mean = 0, and standard deviation = 1
Suppose 1,600 of 2,000 registered voters sampled said they planned to vote for the
Republican candidate for president. Using the 0.95 degree of confidence, what is the
interval estimate for the population proportion (to the nearest 10th of a percent)? -
ANSWER: 78.2% to 81.8%
Which of the following is NOT necessary to determine how large a sample to select
from a population? - ANSWER: The size of the population
A sample mean is the best point estimate of _______. - ANSWER: the population
mean
A sample standard deviation is the best point estimate of the ___________. -
ANSWER: population standard deviation
A confidence interval for a population mean __________. - ANSWER: estimates a
likely interval for a population mean
Knowing the population standard deviation, a 95% confidence interval infers that the
population mean ___________. - ANSWER: is within ±1.96 standard errors of the
sample mean
When a confidence interval for a population mean is constructed from sample data,
__________. - ANSWER: we can conclude, for an infinite number of samples and
corresponding confidence intervals, that the population mean is in a stated
percentage of the intervals
The distribution of Student's t has _________. - ANSWER: a mean of zero and a
standard deviation that depends on the sample size
