ST 560 Final Exam UPDATED ACTUAL
Questions and CORRECT Answers
As the sample size increases, the margin of error - CORRECT ANSWER decreases.
The margin of error in an interval estimate of the population mean is a function of all of the following
except the - CORRECT ANSWER sample mean.
To compute the necessary sample size for an interval estimate of a population proportion, all of the
following procedures are recommended when p is unknown except - CORRECT ANSWER using
0.95 as an estimate.
In order to determine an interval for the mean of a population with unknown standard deviation a sample
of 24 items is selected. The mean of the sample is determined to be 23. The number of degrees of freedom
for reading the t value is - CORRECT ANSWER 23
Male college basketball players have to weigh-in during season and this information is published. We can
therefore know the standard deviation of the entire population. Suppose, however, that we do not know
the population mean and wanted to estimate it. Suppose we took a random sample of 25 male college
basketball players and recorded their weights. The sample mean was found to be 220 lbs. The population
standard deviation is 5 lbs. What is the standard error of the mean? - CORRECT ANSWER 1
We can reduce the margin of error in an interval estimate of p by doing any of the following except -
CORRECT ANSWER increasing the planning value p* to 0.5.
The manager of a grocery store has taken a random sample of 100 customers. The average length of time
it took these 100 customers to check out was 3.0 minutes. It is known that the standard deviation of the
population of checkout times is one minute. The standard error of the mean equals - CORRECT
ANSWER 0.100.
Sales data from a family-owned store shows that 78% of a random sample of 300 customers pay using a
credit card. Compute the 99% confidence interval for the population proportion. - CORRECT
ANSWER 0.71 to 0.84
,An analyst for a cell phone company would like to know the average age at which people obtain their first
cell phone. Past records show a mean of 14 years and a standard deviation of 8 years. What sample size
should be taken so that at 99% confidence the margin of error will be 1 year or less? - CORRECT
ANSWER 425
When the level of confidence decreases, the margin of error - CORRECT ANSWER becomes
smaller.
In general, higher confidence levels provide larger confidence intervals. One way to have high confidence
and a small margin of error is to - CORRECT ANSWER increase the sample size.
From a population that is normally distributed, a sample of 30 elements is selected and the standard
deviation of the sample is computed. For the interval estimation of μ, the proper distribution to use is the -
CORRECT ANSWER t distribution with 29 degrees of freedom.
The CEO of a company wants to estimate the percent of employees that use company computers to go on
Facebook during work hours with 95% confidence. He selects a random sample of 150 of the employees
and finds that 53 of them logged onto Facebook that day. What is the point estimate of the proportion of
the population that logged onto Facebook that day? - CORRECT ANSWER 0.35
A statistics teacher started class one day by drawing the names of 10 students out of a hat and asked them
to do as many pushups as they could. The 10 randomly selected students averaged 15 pushups per person
with a standard deviation of 9 pushups. Suppose the distribution of the population of number of pushups
that can be done is approximately normal. If we would like to capture the population mean with 95%
confidence the margin of error would be - CORRECT ANSWER 2.262*(9 / √10)
A local health center noted that in a sample of 400 patients 80 were referred to them by the local hospital.
What size sample would be required to estimate the proportion of hospital referrals with a margin of error
of 0.04 or less at 95% confidence? - CORRECT ANSWER 385
A researcher is interested in determining the average number of years new teachers remain in the
classroom. If past information shows a standard deviation of 5 years, what size sample should be taken so
that at 95% confidence the margin of error will be 6 months or less? - CORRECT ANSWER 385
,When "s" is used to estimate "σ," the margin of error is computed by using the - CORRECT
ANSWER t distribution.
For a fixed sample size, n, in order to have a higher degree of confidence, the margin of error and the
width of the interval - CORRECT ANSWER must be larger.
The CEO of a company wants to estimate the percent of employees that use company computers to go on
Facebook during work hours with 95% confidence. He selects a random sample of 150 of the employees
and finds that 53 of them logged onto Facebook that day. Compute the 95% confidence interval for the
population proportion. - CORRECT ANSWER 0.35 ± 1.96 * √(0.35(1-0.35))/150
A random sample of 144 observations has a mean of 20, a median of 21, and a mode of 22. The
population standard deviation is known to equal 4.8. The 95.44% confidence interval for the population
mean is - CORRECT ANSWER 19.200 to 20.800.
Suppose a 95% confidence interval, based upon a sample of size 25 for the mean number of hours of
sleep that college students get per night was 5 to 8 hours. How many students should be surveyed in order
to cut the width of the interval down from 3 hours to 1.5 hours? - CORRECT ANSWER 100
An elementary school teacher asked a random sample of 12 of her students what their favorite number is.
Assume the population of responses would follow a normal distribution. The students stated that their
favorite numbers are
2 10 7 4 0 5
6 4 4 6 1 100
What is the appropriate degrees of freedom to use when calculating a 95% confidence interval for μ? -
CORRECT ANSWER 11
Male college basketball players have to weigh-in during season and this information is published. We can
therefore know the standard deviation of the entire population. Suppose, however, that we do not know
the population mean and wanted to estimate it. Suppose we took a random sample of 25 male college
basketball players and recorded their weights. The sample mean was found to be 220 lbs. The population
standard deviation is 5 lbs. The 99% confidence interval is - CORRECT ANSWER 220 ± 2.576 *
(5/(√25)
, The CEO of a company wants to estimate the percent of employees that use company computers to go on
Facebook during work hours with 95% confidence. He selects a random sample of 150 of the employees
and finds that 53 of them logged onto Facebook that day. The CEO would like to cut the margin of error
in half without changing the confidence level. How large of a sample size is needed? - CORRECT
ANSWER 600
A sample of 100 footballs showed an average air pressure of 13 psi. The standard deviation of the
population is known to be 0.25 psi. With a 0.90 probability, the margin of error is approximately -
CORRECT ANSWER 0.041
A sample of 100 footballs showed an average air pressure of 13 psi. The standard deviation of the
population is known to be 0.25 psi. What is the standard error of the mean? - CORRECT
ANSWER 0.025
An elementary school teacher asked a random sample of 12 of her students what their favorite number is.
Assume the population of responses would follow a normal distribution. The students stated that their
favorite numbers are
2 10 7 4 0 5
6 4 4 6 1 100
Suppose we were to create a 95% confidence interval for μ. What effect does the value 100 have on the
width of the confidence interval? - CORRECT ANSWER It makes the interval wider.
The manager of a grocery store has taken a random sample of 100 customers. The average length of time
it took these 100 customers to check out was 3 minutes. It is known that the standard deviation of the
population of checkout times is 1 minute. With a 0.95 probability, the sample mean will provide a margin
of error of 0.196. If we wanted to cut this margin of error in half, how many customers would we need to
include in our sample? - CORRECT ANSWER 400
A statistics teacher started class one day by drawing the names of 10 students out of a hat and asked them
to do as many pushups as they could. The 10 randomly selected students averaged 15 pushups per person
with a standard deviation of 9 pushups. Suppose the distribution of the population of number of pushups
that can be done is approximately normal. What is the standard error of the mean? - CORRECT
ANSWER 2.876
Questions and CORRECT Answers
As the sample size increases, the margin of error - CORRECT ANSWER decreases.
The margin of error in an interval estimate of the population mean is a function of all of the following
except the - CORRECT ANSWER sample mean.
To compute the necessary sample size for an interval estimate of a population proportion, all of the
following procedures are recommended when p is unknown except - CORRECT ANSWER using
0.95 as an estimate.
In order to determine an interval for the mean of a population with unknown standard deviation a sample
of 24 items is selected. The mean of the sample is determined to be 23. The number of degrees of freedom
for reading the t value is - CORRECT ANSWER 23
Male college basketball players have to weigh-in during season and this information is published. We can
therefore know the standard deviation of the entire population. Suppose, however, that we do not know
the population mean and wanted to estimate it. Suppose we took a random sample of 25 male college
basketball players and recorded their weights. The sample mean was found to be 220 lbs. The population
standard deviation is 5 lbs. What is the standard error of the mean? - CORRECT ANSWER 1
We can reduce the margin of error in an interval estimate of p by doing any of the following except -
CORRECT ANSWER increasing the planning value p* to 0.5.
The manager of a grocery store has taken a random sample of 100 customers. The average length of time
it took these 100 customers to check out was 3.0 minutes. It is known that the standard deviation of the
population of checkout times is one minute. The standard error of the mean equals - CORRECT
ANSWER 0.100.
Sales data from a family-owned store shows that 78% of a random sample of 300 customers pay using a
credit card. Compute the 99% confidence interval for the population proportion. - CORRECT
ANSWER 0.71 to 0.84
,An analyst for a cell phone company would like to know the average age at which people obtain their first
cell phone. Past records show a mean of 14 years and a standard deviation of 8 years. What sample size
should be taken so that at 99% confidence the margin of error will be 1 year or less? - CORRECT
ANSWER 425
When the level of confidence decreases, the margin of error - CORRECT ANSWER becomes
smaller.
In general, higher confidence levels provide larger confidence intervals. One way to have high confidence
and a small margin of error is to - CORRECT ANSWER increase the sample size.
From a population that is normally distributed, a sample of 30 elements is selected and the standard
deviation of the sample is computed. For the interval estimation of μ, the proper distribution to use is the -
CORRECT ANSWER t distribution with 29 degrees of freedom.
The CEO of a company wants to estimate the percent of employees that use company computers to go on
Facebook during work hours with 95% confidence. He selects a random sample of 150 of the employees
and finds that 53 of them logged onto Facebook that day. What is the point estimate of the proportion of
the population that logged onto Facebook that day? - CORRECT ANSWER 0.35
A statistics teacher started class one day by drawing the names of 10 students out of a hat and asked them
to do as many pushups as they could. The 10 randomly selected students averaged 15 pushups per person
with a standard deviation of 9 pushups. Suppose the distribution of the population of number of pushups
that can be done is approximately normal. If we would like to capture the population mean with 95%
confidence the margin of error would be - CORRECT ANSWER 2.262*(9 / √10)
A local health center noted that in a sample of 400 patients 80 were referred to them by the local hospital.
What size sample would be required to estimate the proportion of hospital referrals with a margin of error
of 0.04 or less at 95% confidence? - CORRECT ANSWER 385
A researcher is interested in determining the average number of years new teachers remain in the
classroom. If past information shows a standard deviation of 5 years, what size sample should be taken so
that at 95% confidence the margin of error will be 6 months or less? - CORRECT ANSWER 385
,When "s" is used to estimate "σ," the margin of error is computed by using the - CORRECT
ANSWER t distribution.
For a fixed sample size, n, in order to have a higher degree of confidence, the margin of error and the
width of the interval - CORRECT ANSWER must be larger.
The CEO of a company wants to estimate the percent of employees that use company computers to go on
Facebook during work hours with 95% confidence. He selects a random sample of 150 of the employees
and finds that 53 of them logged onto Facebook that day. Compute the 95% confidence interval for the
population proportion. - CORRECT ANSWER 0.35 ± 1.96 * √(0.35(1-0.35))/150
A random sample of 144 observations has a mean of 20, a median of 21, and a mode of 22. The
population standard deviation is known to equal 4.8. The 95.44% confidence interval for the population
mean is - CORRECT ANSWER 19.200 to 20.800.
Suppose a 95% confidence interval, based upon a sample of size 25 for the mean number of hours of
sleep that college students get per night was 5 to 8 hours. How many students should be surveyed in order
to cut the width of the interval down from 3 hours to 1.5 hours? - CORRECT ANSWER 100
An elementary school teacher asked a random sample of 12 of her students what their favorite number is.
Assume the population of responses would follow a normal distribution. The students stated that their
favorite numbers are
2 10 7 4 0 5
6 4 4 6 1 100
What is the appropriate degrees of freedom to use when calculating a 95% confidence interval for μ? -
CORRECT ANSWER 11
Male college basketball players have to weigh-in during season and this information is published. We can
therefore know the standard deviation of the entire population. Suppose, however, that we do not know
the population mean and wanted to estimate it. Suppose we took a random sample of 25 male college
basketball players and recorded their weights. The sample mean was found to be 220 lbs. The population
standard deviation is 5 lbs. The 99% confidence interval is - CORRECT ANSWER 220 ± 2.576 *
(5/(√25)
, The CEO of a company wants to estimate the percent of employees that use company computers to go on
Facebook during work hours with 95% confidence. He selects a random sample of 150 of the employees
and finds that 53 of them logged onto Facebook that day. The CEO would like to cut the margin of error
in half without changing the confidence level. How large of a sample size is needed? - CORRECT
ANSWER 600
A sample of 100 footballs showed an average air pressure of 13 psi. The standard deviation of the
population is known to be 0.25 psi. With a 0.90 probability, the margin of error is approximately -
CORRECT ANSWER 0.041
A sample of 100 footballs showed an average air pressure of 13 psi. The standard deviation of the
population is known to be 0.25 psi. What is the standard error of the mean? - CORRECT
ANSWER 0.025
An elementary school teacher asked a random sample of 12 of her students what their favorite number is.
Assume the population of responses would follow a normal distribution. The students stated that their
favorite numbers are
2 10 7 4 0 5
6 4 4 6 1 100
Suppose we were to create a 95% confidence interval for μ. What effect does the value 100 have on the
width of the confidence interval? - CORRECT ANSWER It makes the interval wider.
The manager of a grocery store has taken a random sample of 100 customers. The average length of time
it took these 100 customers to check out was 3 minutes. It is known that the standard deviation of the
population of checkout times is 1 minute. With a 0.95 probability, the sample mean will provide a margin
of error of 0.196. If we wanted to cut this margin of error in half, how many customers would we need to
include in our sample? - CORRECT ANSWER 400
A statistics teacher started class one day by drawing the names of 10 students out of a hat and asked them
to do as many pushups as they could. The 10 randomly selected students averaged 15 pushups per person
with a standard deviation of 9 pushups. Suppose the distribution of the population of number of pushups
that can be done is approximately normal. What is the standard error of the mean? - CORRECT
ANSWER 2.876
