STAT 121: FINAL PRACTICE EXAM TEST QUESTIONS
WITH VERIFIED ANSWERS
Smudge pots are sometimes used to protect orchards from frost. Two types of smudge
pots are to be compared to determine which has the longest average burn time. Ten
pots of each type are randomly selected for the study. These twenty pots will be lit and
the burn time for each recorded. What statistical procedure should be used to analyze
these data? - Answers - Two-sample t test for means
What is the symbol for the difference between two population means? - Answers -
μ1−μ2
1400 bald male subjects were in a study to determine whether Rogaine is effective in
stimulating hair growth. The subjects were randomly divided into two groups: one group
having a placebo preparation applied containing no Rogaine and the other group having
Rogaine applied. Neither the subjects nor the people recording the results knew who
received the Rogaine and who did not. At the end of the treatment period, each subject
was examined to determine whether he experience new hair growth. The researchers
want to determine whether the proportion of those in the Rogaine treatment group who
experienced new hair growth exceeded the proportion of those in the control group.
What are the appropriate hypotheses? - Answers - H0 : pR = pc versus Ha : pR > pC
Suppose you want to estimate the proportion of voters who will vote for George Smith, a
candidate for state representative. How many should you sample in order to estimate p
with a margin of error of 0.05 (5%) and 95% confidence? - Answers - 385
A local television network affiliate, WKSU, has recently remodeled its broadcast studio
and changed its news anchor-persons. The station manager now wants to estimate the
percentage of the viewing audience who currently watch its new broadcast. Which one
of the following formulas should the station manager use to obtain the 99% confidence
interval estimate that he desires? - Answers - Use this formula.
Which one of the following represents the parameter estimated with a 99% confidence
interval for difference in proportions? - Answers - p1 − p2
If we were to test the hypotheses H0 : p = 0.7 versus Ha : p > 0.7 using sample results
of p-hat = 0.80 from a sample of size 100, what is the value we should use for the
standard deviation of the sampling distribution of p-hat in the test statistic? - Answers -
sq root of p(1-p)/n = 0.0458
Use this information to answer the next two questions.
A quality inspector checks a large truckload of potatoes to determine the proportion of
defective potatoes. She tests the hypotheses H0 : p = .06 versus 0 Ha : p > 0.06 and
,will accept the shipment unless she has sufficient evidence that the proportion of
defective potatoes significantly exceeds 6%. She plans to randomly sample 100
potatoes.
Is this sample size large enough to perform a one-sample z test for the proportion? -
Answers - No, because 100(.06) < 10.
Use this information to answer the next two questions.
A quality inspector checks a large truckload of potatoes to determine the proportion of
defective potatoes. She tests the hypotheses H0 : p = .06 versus 0 Ha : p > 0.06 and
will accept the shipment unless she has sufficient evidence that the proportion of
defective potatoes significantly exceeds 6%. She plans to randomly sample 100
potatoes.
Assume that the quality inspector takes a random sample of potatoes that is large
enough to satisfy the conditions and finds p-value = 0.118. Should she accept the
shipment at α = 0.05 ? Why or why not? - Answers - Yes, because we fail to reject H0 at
α = 0.05.
Use this information to answer the next two questions: A company asserts that 80% of
the customers who purchase its special lawn mower will have no repairs during the first
two years of ownership. Your personal study of 100 randomly selected owners found 70
lasted the first two years without repair expenses.
What statistical procedure should be used to test the company's claim? - Answers -
One-sample z test for proportions
Use this information to answer the next two questions: A company asserts that 80% of
the customers who purchase its special lawn mower will have no repairs during the first
two years of ownership. Your personal study of 100 randomly selected owners found 70
lasted the first two years without repair expenses.
Can you use the standard Normal table to compute the probability that 70% or fewer in
the sample lasted the two years without repair expenses? Why or why not? - Answers -
Yes, because both of the following are met: np ≥ 10, n(1 − p) ≥ 10.
Referring to the information above, what is the mean and standard deviation of the
sampling distribution of for samples of size n = 100 if p = 0.80? - Answers - 0.80 and
0.04. Where, the SD is sqrt of p(1-p)/100 = .04 and the parameter is the same as the
mean of the sampling distribution of p hat.
Suppose we are testing H0 : p = 0.5 versus Ha : p ≠ 0.5 and the test statistic from our
random sample results is z = 1.83. What can we conclude at the 5% level of
significance? - Answers - We have insufficient evidence to conclude that the population
proportion is significantly different from 0.5.
, A multimedia program designed to improve dietary behavior among low-income women
was evaluated by comparing women who were randomly assigned to intervention and
control groups. The intervention was a 30-minute session in a computer kiosk in the
Food Stamp office. One of the outcomes was the score on a knowledge test taken
about two months after the program. In testing whether the women in the intervention
group scored higher than the women in the control group on average, the following
results were obtained using Stat Crunch.
At α = 0.5 , what should we conclude? - Answers - The mean score of women in the
intervention group is significantly greater than the mean score of women in the control
group.
A study was carried out to investigate possible effects of ultrasound on the birth weight
of babies. The average birth weight of babies born at Johns Hopkins Hospital in a
certain year whose mothers had received an ultrasound examination during pregnancy
was compared to the average birth weight of babies born in the same hospital in the
same year whose mothers had not received an ultrasound examination. Mothers were
randomly selected from each group to estimate the respective group's average. What
type of study is this? - Answers - An observational study
A company's news release for a diet product reported a study showing that most people
who lose weight using their product keep it off. The study was based on a sample of 20
graduates of the company's program, who endorse it in commercials. The results of the
sample are probably ________. - Answers - Biased, overstating the effectiveness of the
product.
Which one of the following is not a valid sample for collecting data for inference? -
Answers - A convenience sample
In order to assess the opinions of BYU students about a proposed library remodel, a
reporter interviews the first ten people entering the library who are willing to express an
opinion. What type of study is this? - Answers - An observational study based on a
convenience sample
Use this information to answer the next two questions.
In a study of the effect of nitrites on bacteria, researchers measured the rate of uptake
of an amino acid for 30 cultures of bacteria growing in a solution. Here is the resulting
stem plot:
What is the value of the median? - Answers - 7950
Use this information to answer the next two questions.
In a study of the effect of nitrites on bacteria, researchers measured the rate of uptake
of an amino acid for 30 cultures of bacteria growing in a solution. Here is the resulting
stem plot:
WITH VERIFIED ANSWERS
Smudge pots are sometimes used to protect orchards from frost. Two types of smudge
pots are to be compared to determine which has the longest average burn time. Ten
pots of each type are randomly selected for the study. These twenty pots will be lit and
the burn time for each recorded. What statistical procedure should be used to analyze
these data? - Answers - Two-sample t test for means
What is the symbol for the difference between two population means? - Answers -
μ1−μ2
1400 bald male subjects were in a study to determine whether Rogaine is effective in
stimulating hair growth. The subjects were randomly divided into two groups: one group
having a placebo preparation applied containing no Rogaine and the other group having
Rogaine applied. Neither the subjects nor the people recording the results knew who
received the Rogaine and who did not. At the end of the treatment period, each subject
was examined to determine whether he experience new hair growth. The researchers
want to determine whether the proportion of those in the Rogaine treatment group who
experienced new hair growth exceeded the proportion of those in the control group.
What are the appropriate hypotheses? - Answers - H0 : pR = pc versus Ha : pR > pC
Suppose you want to estimate the proportion of voters who will vote for George Smith, a
candidate for state representative. How many should you sample in order to estimate p
with a margin of error of 0.05 (5%) and 95% confidence? - Answers - 385
A local television network affiliate, WKSU, has recently remodeled its broadcast studio
and changed its news anchor-persons. The station manager now wants to estimate the
percentage of the viewing audience who currently watch its new broadcast. Which one
of the following formulas should the station manager use to obtain the 99% confidence
interval estimate that he desires? - Answers - Use this formula.
Which one of the following represents the parameter estimated with a 99% confidence
interval for difference in proportions? - Answers - p1 − p2
If we were to test the hypotheses H0 : p = 0.7 versus Ha : p > 0.7 using sample results
of p-hat = 0.80 from a sample of size 100, what is the value we should use for the
standard deviation of the sampling distribution of p-hat in the test statistic? - Answers -
sq root of p(1-p)/n = 0.0458
Use this information to answer the next two questions.
A quality inspector checks a large truckload of potatoes to determine the proportion of
defective potatoes. She tests the hypotheses H0 : p = .06 versus 0 Ha : p > 0.06 and
,will accept the shipment unless she has sufficient evidence that the proportion of
defective potatoes significantly exceeds 6%. She plans to randomly sample 100
potatoes.
Is this sample size large enough to perform a one-sample z test for the proportion? -
Answers - No, because 100(.06) < 10.
Use this information to answer the next two questions.
A quality inspector checks a large truckload of potatoes to determine the proportion of
defective potatoes. She tests the hypotheses H0 : p = .06 versus 0 Ha : p > 0.06 and
will accept the shipment unless she has sufficient evidence that the proportion of
defective potatoes significantly exceeds 6%. She plans to randomly sample 100
potatoes.
Assume that the quality inspector takes a random sample of potatoes that is large
enough to satisfy the conditions and finds p-value = 0.118. Should she accept the
shipment at α = 0.05 ? Why or why not? - Answers - Yes, because we fail to reject H0 at
α = 0.05.
Use this information to answer the next two questions: A company asserts that 80% of
the customers who purchase its special lawn mower will have no repairs during the first
two years of ownership. Your personal study of 100 randomly selected owners found 70
lasted the first two years without repair expenses.
What statistical procedure should be used to test the company's claim? - Answers -
One-sample z test for proportions
Use this information to answer the next two questions: A company asserts that 80% of
the customers who purchase its special lawn mower will have no repairs during the first
two years of ownership. Your personal study of 100 randomly selected owners found 70
lasted the first two years without repair expenses.
Can you use the standard Normal table to compute the probability that 70% or fewer in
the sample lasted the two years without repair expenses? Why or why not? - Answers -
Yes, because both of the following are met: np ≥ 10, n(1 − p) ≥ 10.
Referring to the information above, what is the mean and standard deviation of the
sampling distribution of for samples of size n = 100 if p = 0.80? - Answers - 0.80 and
0.04. Where, the SD is sqrt of p(1-p)/100 = .04 and the parameter is the same as the
mean of the sampling distribution of p hat.
Suppose we are testing H0 : p = 0.5 versus Ha : p ≠ 0.5 and the test statistic from our
random sample results is z = 1.83. What can we conclude at the 5% level of
significance? - Answers - We have insufficient evidence to conclude that the population
proportion is significantly different from 0.5.
, A multimedia program designed to improve dietary behavior among low-income women
was evaluated by comparing women who were randomly assigned to intervention and
control groups. The intervention was a 30-minute session in a computer kiosk in the
Food Stamp office. One of the outcomes was the score on a knowledge test taken
about two months after the program. In testing whether the women in the intervention
group scored higher than the women in the control group on average, the following
results were obtained using Stat Crunch.
At α = 0.5 , what should we conclude? - Answers - The mean score of women in the
intervention group is significantly greater than the mean score of women in the control
group.
A study was carried out to investigate possible effects of ultrasound on the birth weight
of babies. The average birth weight of babies born at Johns Hopkins Hospital in a
certain year whose mothers had received an ultrasound examination during pregnancy
was compared to the average birth weight of babies born in the same hospital in the
same year whose mothers had not received an ultrasound examination. Mothers were
randomly selected from each group to estimate the respective group's average. What
type of study is this? - Answers - An observational study
A company's news release for a diet product reported a study showing that most people
who lose weight using their product keep it off. The study was based on a sample of 20
graduates of the company's program, who endorse it in commercials. The results of the
sample are probably ________. - Answers - Biased, overstating the effectiveness of the
product.
Which one of the following is not a valid sample for collecting data for inference? -
Answers - A convenience sample
In order to assess the opinions of BYU students about a proposed library remodel, a
reporter interviews the first ten people entering the library who are willing to express an
opinion. What type of study is this? - Answers - An observational study based on a
convenience sample
Use this information to answer the next two questions.
In a study of the effect of nitrites on bacteria, researchers measured the rate of uptake
of an amino acid for 30 cultures of bacteria growing in a solution. Here is the resulting
stem plot:
What is the value of the median? - Answers - 7950
Use this information to answer the next two questions.
In a study of the effect of nitrites on bacteria, researchers measured the rate of uptake
of an amino acid for 30 cultures of bacteria growing in a solution. Here is the resulting
stem plot:
