Test Bank for Business Statistics (All
Chapters included)
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? - answers 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? - answers 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? - answers 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? -
answers 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? - answers 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? -
answers 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? - answers 50,000
What is the interpretation of a 96% confidence level? - answers 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? - answers All apply
What kind of distribution is the t distribution? - answers Continuous
How is the t distribution similar to the standard z distribution? - answers 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? - answers 19
Of the following characteristics, the t distribution and z distribution are the same in all
BUT one. Which one is it? - answers 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)? -
answers 78.2% to 81.8%
Which of the following is NOT necessary to determine how large a sample to select
from a population? - answers The size of the population
A sample mean is the best point estimate of _______. - answers the population mean
A sample standard deviation is the best point estimate of the ___________. - answers
population standard deviation
A confidence interval for a population mean __________. - answers estimates a likely
interval for a population mean
Knowing the population standard deviation, a 95% confidence interval infers that the
population mean ___________. - answers is within ±1.96 standard errors of the sample
mean
When a confidence interval for a population mean is constructed from sample data,
__________. - answers 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 _________. - answers a mean of zero and a standard
deviation that depends on the sample size
The distribution of Student's t is ________. - answers symmetrical
,When using Student's t to compute an interval estimate, ___________. - answers we
assume that the samples are collected from normally distributed populations
A random sample of 42 college graduates revealed that they worked an average of 5.5
years on the job before being promoted. The sample standard deviation was 1.1 years.
Using the 0.99 degree of confidence, what is the confidence interval for the population
mean? - answers 5.04 and 5.96
When we use a confidence interval to reach a conclusion about the population mean,
we are applying a type of reasoning or logic called __________. - answers statistical
inference
A local company wants to evaluate their quality of service by surveying their customers.
Their budget limits the number of surveys to 100. What is their maximum error of the
estimated mean quality for a 95% level of confidence and an estimated standard
deviation of 5? - answers 0.9604
A local retail company wants to estimate the mean amount spent by customers. Their
store's budget limits the number of surveys to 225. What is their maximum error of the
estimated mean amount spent for a 99% level of confidence and an estimated standard
deviation of $10.00? - answers $1.72
A university surveyed recent graduates of the English Department for their starting
salaries. Four hundred graduates returned the survey. The average salary was $25,000,
with a standard deviation of $2,500. What is the best point estimate of the population
mean? - answers $25,000
A university surveyed recent graduates of the English Department for their starting
salaries. Four hundred graduates returned the survey. The average salary was $25,000.
The population standard deviation was $2,500. What is the 95% confidence interval for
the mean salary of all graduates from the English Department? - answers [$24,755,
$25,245]
A university surveyed recent graduates of the English Department for their starting
salaries. Four hundred graduates returned the survey. The average salary was $25,000.
The population standard deviation is $2,500. A 95% confidence interval is constructed.
What does the confidence interval mean? - answers The likelihood that any confidence
interval based on a sample of 400 graduates will contain the population mean is 0.95.
A survey of an urban university (population of 25,450) showed that 870 of 1,100
students sampled supported a fee increase to fund improvements to the student
recreation center. Using the 95% level of confidence, what is the confidence interval for
the proportion of students supporting the fee increase? - answers [0.767, 0.815]
A survey of an urban university (population of 25,450) showed that 870 of 1,100
students sampled supported a fee increase to fund improvements to the student
, recreation center. Using the 99% level of confidence, what is the confidence interval for
the proportion of students supporting the fee increase? - answers [0.759, 0.823]
University officials say that at least 70% of the voting student population supports a fee
increase. If the 95% confidence interval estimating the proportion of students supporting
the fee increase is [0.75, 0.85], what conclusion can be drawn? - answers The interval
estimate is above 70%, so infer that it will be supported.
A group of statistics students decided to conduct a survey at their university to find the
average (mean) amount of time students spent studying per week. Assuming a
population standard deviation of six hours, what is the required sample size if the error
should be less than a half hour with a 95% level of confidence? - answers 554
A group of statistics students decided to conduct a survey at their university to find the
average (mean) amount of time students spent studying per week. Assuming a
population standard deviation of three hours, what is the required sample size if the
error should be less than a half hour with a 99% level of confidence? - answers 239
A group of statistics students decided to conduct a survey at their university to estimate
the average (mean) amount of time students spent studying per week. They sampled
554 students and found a mean of 22.3 hours per week. Assuming a population
standard deviation of six hours, what is the 95% level of confidence? - answers [21.80,
22.80]
A group of statistics students decided to conduct a survey at their university to find the
average (mean) amount of time students spent studying per week. They sampled 240
students and found a mean of 22.3 hours per week. Assuming a population standard
deviation of six hours, what is the 99% level of confidence? - answers [21.30, 23.30]
A research firm wants to compute an interval estimate with 90% confidence for the
mean time to complete an employment test. Assuming a population standard deviation
of three hours, what is the required sample size if the error should be less than a half
hour? - answers 98
A survey of 50 retail stores revealed that the average price of a microwave was $375,
with a sample standard deviation of $20. Assuming the population is normally
distributed, what is the 95% confidence interval to estimate the true cost of the
microwave? - answers $369.31 to $380.69
A survey of 50 retail stores revealed that the average price of a microwave was $375
with a sample standard deviation of $20. Assuming the population is normally
distributed, what is the 99% confidence interval to estimate the true cost of the
microwave? - answers $367.42 to $382.58
A survey of 50 retail stores revealed that the average price of a microwave was $375,
with a sample standard deviation of $20. If 90% and 95% confidence intervals were
Chapters included)
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? - answers 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? - answers 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? - answers 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? -
answers 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? - answers 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? -
answers 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? - answers 50,000
What is the interpretation of a 96% confidence level? - answers 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? - answers All apply
What kind of distribution is the t distribution? - answers Continuous
How is the t distribution similar to the standard z distribution? - answers 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? - answers 19
Of the following characteristics, the t distribution and z distribution are the same in all
BUT one. Which one is it? - answers 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)? -
answers 78.2% to 81.8%
Which of the following is NOT necessary to determine how large a sample to select
from a population? - answers The size of the population
A sample mean is the best point estimate of _______. - answers the population mean
A sample standard deviation is the best point estimate of the ___________. - answers
population standard deviation
A confidence interval for a population mean __________. - answers estimates a likely
interval for a population mean
Knowing the population standard deviation, a 95% confidence interval infers that the
population mean ___________. - answers is within ±1.96 standard errors of the sample
mean
When a confidence interval for a population mean is constructed from sample data,
__________. - answers 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 _________. - answers a mean of zero and a standard
deviation that depends on the sample size
The distribution of Student's t is ________. - answers symmetrical
,When using Student's t to compute an interval estimate, ___________. - answers we
assume that the samples are collected from normally distributed populations
A random sample of 42 college graduates revealed that they worked an average of 5.5
years on the job before being promoted. The sample standard deviation was 1.1 years.
Using the 0.99 degree of confidence, what is the confidence interval for the population
mean? - answers 5.04 and 5.96
When we use a confidence interval to reach a conclusion about the population mean,
we are applying a type of reasoning or logic called __________. - answers statistical
inference
A local company wants to evaluate their quality of service by surveying their customers.
Their budget limits the number of surveys to 100. What is their maximum error of the
estimated mean quality for a 95% level of confidence and an estimated standard
deviation of 5? - answers 0.9604
A local retail company wants to estimate the mean amount spent by customers. Their
store's budget limits the number of surveys to 225. What is their maximum error of the
estimated mean amount spent for a 99% level of confidence and an estimated standard
deviation of $10.00? - answers $1.72
A university surveyed recent graduates of the English Department for their starting
salaries. Four hundred graduates returned the survey. The average salary was $25,000,
with a standard deviation of $2,500. What is the best point estimate of the population
mean? - answers $25,000
A university surveyed recent graduates of the English Department for their starting
salaries. Four hundred graduates returned the survey. The average salary was $25,000.
The population standard deviation was $2,500. What is the 95% confidence interval for
the mean salary of all graduates from the English Department? - answers [$24,755,
$25,245]
A university surveyed recent graduates of the English Department for their starting
salaries. Four hundred graduates returned the survey. The average salary was $25,000.
The population standard deviation is $2,500. A 95% confidence interval is constructed.
What does the confidence interval mean? - answers The likelihood that any confidence
interval based on a sample of 400 graduates will contain the population mean is 0.95.
A survey of an urban university (population of 25,450) showed that 870 of 1,100
students sampled supported a fee increase to fund improvements to the student
recreation center. Using the 95% level of confidence, what is the confidence interval for
the proportion of students supporting the fee increase? - answers [0.767, 0.815]
A survey of an urban university (population of 25,450) showed that 870 of 1,100
students sampled supported a fee increase to fund improvements to the student
, recreation center. Using the 99% level of confidence, what is the confidence interval for
the proportion of students supporting the fee increase? - answers [0.759, 0.823]
University officials say that at least 70% of the voting student population supports a fee
increase. If the 95% confidence interval estimating the proportion of students supporting
the fee increase is [0.75, 0.85], what conclusion can be drawn? - answers The interval
estimate is above 70%, so infer that it will be supported.
A group of statistics students decided to conduct a survey at their university to find the
average (mean) amount of time students spent studying per week. Assuming a
population standard deviation of six hours, what is the required sample size if the error
should be less than a half hour with a 95% level of confidence? - answers 554
A group of statistics students decided to conduct a survey at their university to find the
average (mean) amount of time students spent studying per week. Assuming a
population standard deviation of three hours, what is the required sample size if the
error should be less than a half hour with a 99% level of confidence? - answers 239
A group of statistics students decided to conduct a survey at their university to estimate
the average (mean) amount of time students spent studying per week. They sampled
554 students and found a mean of 22.3 hours per week. Assuming a population
standard deviation of six hours, what is the 95% level of confidence? - answers [21.80,
22.80]
A group of statistics students decided to conduct a survey at their university to find the
average (mean) amount of time students spent studying per week. They sampled 240
students and found a mean of 22.3 hours per week. Assuming a population standard
deviation of six hours, what is the 99% level of confidence? - answers [21.30, 23.30]
A research firm wants to compute an interval estimate with 90% confidence for the
mean time to complete an employment test. Assuming a population standard deviation
of three hours, what is the required sample size if the error should be less than a half
hour? - answers 98
A survey of 50 retail stores revealed that the average price of a microwave was $375,
with a sample standard deviation of $20. Assuming the population is normally
distributed, what is the 95% confidence interval to estimate the true cost of the
microwave? - answers $369.31 to $380.69
A survey of 50 retail stores revealed that the average price of a microwave was $375
with a sample standard deviation of $20. Assuming the population is normally
distributed, what is the 99% confidence interval to estimate the true cost of the
microwave? - answers $367.42 to $382.58
A survey of 50 retail stores revealed that the average price of a microwave was $375,
with a sample standard deviation of $20. If 90% and 95% confidence intervals were
