STAT 200 Week 6 Homework Solution Correct Answers
Week 6 homework solutions on key statistical concepts.
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STAT 200 Week 6 Homework Solution Correct Answers
18. You choose an alpha level of .01 and then analyze your data.
a. What is the probability that you will make a Type I error given that the null
hypothesis is true?
b. What is the probability that you will make a Type I error given that the null
hypothesis is false?
7. Below are data showing the results of six subjects on a memory test. The three
scores per subject are their scores on three trials (a, b, and c) of a memory task.
Are the subjects get- ting better each trial? Test the linear effect of trial for the data.
a. Compute L for each subject using the contrast weights -1, 0, and 1. That is,
compute (-1)(a) + (0)(b) + (1)(c) for each subject.
b. Compute a one-sample t-test on this column (with the L values for each subject)
you created.
13. You are conducting a study to see if students do better when they study all at
once or in intervals. One group of 12 participants took a test after studying for one
hour continuously. The other group of 12 participants took a test after studying for
three twenty minute sessions. The first group had a mean score of 75 and a
variance of 120. The second group had a mean score of 86 and a variance of 100.
a. What is the calculated t value? Are the mean test scores of these two groups
significantly different at the .05 level?
b. What would the t value be if there were only 6 participants in each group? Would
the scores be significant at the .05 level?
18. You choose an alpha level of .01 and then analyze your data.
a. What is the probability that you will make a Type I error given that the null
hypothesis is true?
b. What is the probability that you will make a Type I error given that the null
hypothesis is false?
7. Below are data showing the results of six subjects on a memory test. The three
scores per subject are their scores on three trials (a, b, and c) of a memory task.
Are the subjects get- ting better each trial? Test the linear effect of trial for the data.
a. Compute L for each subject using the contrast weights -1, 0, and 1. That is,
compute (-1)(a) + (0)(b) + (1)(c) for each subject.
b. Compute a one-sample t-test on this column (with the L values for each subject)
you created.
13. You are conducting a study to see if students do better when they study all at
once or in intervals. One group of 12 participants took a test after studying for one
hour continuously. The other group of 12 participants took a test after studying for
three twenty minute sessions. The first group had a mean score of 75 and a
variance of 120. The second group had a mean score of 86 and a variance of 100.
a. What is the calculated t value? Are the mean test scores of these two groups
significantly different at the .05 level?
b. What would the t value be if there were only 6 participants in each group? Would
the scores be significant at the .05 level?
4. Rank the following in terms of power.
65. Previously, an organization reported that teenagers spent 4.5 hours per week, on
average, on the phone. The organization thinks that, currently, the mean is higher.
Fifteen randomly chosen teenagers were asked how many hours per week they spend
on the phone. The sample mean was 4.75 hours with a sample standard deviation of
2.0. Conduct a hypothesis test.
71. Previously, an organization reported that teenagers spent 4.5 hours per week, on
average, on the phone. The organization thinks that, currently, the mean is higher.
Fifteen randomly chosen teenagers were asked how many hours per week they spend
on the phone. The sample mean was 4.75 hours with a sample standard deviation of
2.0. Conduct a hypothesis test, the Type I error is:
a. to conclude that the current mean hours per week is higher than 4.5, when in fact,
it is higher
b. to conclude that the current mean hours per week is higher than 4.5, when in fact,
it is the same
c. to conclude that the mean hours per week currently is 4.5, when in fact, it is
higher
d. to conclude that the mean hours per week currently is no higher than 4.5, when in
fact, it is not higher
77. An article in the San Jose Mercury News stated that students in the California
state university system take 4.5 years, on average, to finish their undergraduate
65. Previously, an organization reported that teenagers spent 4.5 hours per week, on
average, on the phone. The organization thinks that, currently, the mean is higher.
Fifteen randomly chosen teenagers were asked how many hours per week they spend
on the phone. The sample mean was 4.75 hours with a sample standard deviation of
2.0. Conduct a hypothesis test.
71. Previously, an organization reported that teenagers spent 4.5 hours per week, on
average, on the phone. The organization thinks that, currently, the mean is higher.
Fifteen randomly chosen teenagers were asked how many hours per week they spend
on the phone. The sample mean was 4.75 hours with a sample standard deviation of
2.0. Conduct a hypothesis test, the Type I error is:
a. to conclude that the current mean hours per week is higher than 4.5, when in fact,
it is higher
b. to conclude that the current mean hours per week is higher than 4.5, when in fact,
it is the same
c. to conclude that the mean hours per week currently is 4.5, when in fact, it is
higher
d. to conclude that the mean hours per week currently is no higher than 4.5, when in
fact, it is not higher
77. An article in the San Jose Mercury News stated that students in the California
state university system take 4.5 years, on average, to finish their undergraduate
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University
University of Maryland
Subject
Statistics