They selected a random sample of 30 students from their medium-sized high school to participate. Each subject was given 10 minutes to memorize two dif- ferent lists of 20 words, once while listening to music and once in silence. The order of the two word lists was determined at random; so was the order of the treatments. The difference in the number of words recalled (music – silence) was recorded for each subject. A paired t test on the differences yielded t = -3.01 and P-value 0.0027.

Glencoe Algebra 1, Student Edition, 9780079039897, 0079039898, 2018
18th Edition
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Author:Carter
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Chapter10: Statistics
Section10.5: Comparing Sets Of Data
Problem 26PFA
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Answer question 88

They selected a random sample of 30 students from
their medium-sized high school to participate. Each
subject was given 10 minutes to memorize two dif-
ferent lists of 20 words, once while listening to music
and once in silence. The order of the two word lists
was determined at random; so was the order of the
treatments. The difference in the number of words
recalled (music
•..
Subject
Unscented
Scented
68.47
49.00
6
32.43
43.23
7
43.70
44.57
8
37.10
28.40
9.
31.17
28.23
silence) was recorded for each
10
51.23
68.47
subject. A paired t test on the differences yielded
t = -3.01 and P-value = 0.0027.
11
65.40
51.10
12
58.93
83.50
(a) State appropriate hypotheses for the paired t test. Be
sure to define your parameter.
13
54.47
38.30
14
43.53
51.37
(b) What are the degrees of freedom for the paired t test?
15
37.93
29.33
(c) Interpret the P-value in context. What conclusion
should the students draw?
16
43.50
54.27
17
87.70
62.73
(d) Describe a Type I error and a Type II error in this set-
ting. Which mistake could students have made based
18
53.53
58.00
19
64.30
52.40
on your answer to part (c)?
20
47.37
53.63
89. The power of tomatoes Refer to Exercise 87.
Explain two ways that the researchers could have
increased the power of the test to detect u = 0.5.
21
53.67
47.00
(a) Explain why it was important to randomly assign the
order in which each subject used the two masks.
(b) Do these data provide convincing evidence that the
floral scent improved performance, on average?
90. Music and memory Refer to Exercise 88. Which of the
following changes would give the test a higher power to
detect u = -1: using a =
0.01 or α
0.10? Explain.
87. Growing tomatoes Researchers suspect that Variety A
tomato plants have a higher average yield than Variety
B tomato plants. To find out, researchers randomly
select 10 Variety A and 10 Variety B tomato plants.
Then the researchers divide in half each of 10 small
91. Significance and sample size A study with 5000
subjects reported a result that was statistically signifi-
cant at the 5% level. Explain why this result might
not be particularly large or important.
plots of land in different locations. For each plot, a
coin toss determines which half of the plot gets a Va-
riety A plant; a Variety B plant goes in the other half.
After harvest, they compare the yield in pounds for
the plants at each location. The 10 differences in yield
(Variety A – Variety B) are recorded. A graph of the
differences looks roughly symmetric and single-peaked
with no outliers. A paired t test on the differences
yields t = 1.295 and P-value = 0.1138.
92. Sampling shoppers A marketing consultant
observes 50 consecutive shoppers at a supermarket,
recording how much each shopper spends in the
store. Explain why it would not be wise to use these
data to carry out a significance test about the mean
amount spent by all shoppers at this supermarket.
93. Do you have ESP? A researcher looking for evidence
of extrasensory perception (ESP) tests 500 subjects.
Four of these subjects do significantly better (P < 0.01)
than random guessing.
(a) State appropriate hypotheses for the paired t test. Be
sure to define your parameter.
(a) Is it proper to conclude that these four people have
ESP? Explain your answer.
(b) What are the degrees of freedom for the paired t test?
(c) Interpret the P-value in context. What conclusion
should the researchers draw?
(b) What should the researcher now do to test whether
any of these four subjects have ESP?
94. Ages of presidents Joe is writing a report on the
backgrounds of American presidents. He looks up
the ages of all the presidents when they entered
office. Because Joe took a statistics course, he uses
these numbers to perform a significance test about
the mean age
makes no sense.
(d) Describe a Type I error and a Type II error in this
setting. Which mistake could researchers have made
based on your answer to part (c)?
88. Music and memory Does listening to music while
studying hinder students' learning? Two AP® Sta-
tistics students designed an experiment to find out.
of all U.S. presidents. Explain why this
Transcribed Image Text:They selected a random sample of 30 students from their medium-sized high school to participate. Each subject was given 10 minutes to memorize two dif- ferent lists of 20 words, once while listening to music and once in silence. The order of the two word lists was determined at random; so was the order of the treatments. The difference in the number of words recalled (music •.. Subject Unscented Scented 68.47 49.00 6 32.43 43.23 7 43.70 44.57 8 37.10 28.40 9. 31.17 28.23 silence) was recorded for each 10 51.23 68.47 subject. A paired t test on the differences yielded t = -3.01 and P-value = 0.0027. 11 65.40 51.10 12 58.93 83.50 (a) State appropriate hypotheses for the paired t test. Be sure to define your parameter. 13 54.47 38.30 14 43.53 51.37 (b) What are the degrees of freedom for the paired t test? 15 37.93 29.33 (c) Interpret the P-value in context. What conclusion should the students draw? 16 43.50 54.27 17 87.70 62.73 (d) Describe a Type I error and a Type II error in this set- ting. Which mistake could students have made based 18 53.53 58.00 19 64.30 52.40 on your answer to part (c)? 20 47.37 53.63 89. The power of tomatoes Refer to Exercise 87. Explain two ways that the researchers could have increased the power of the test to detect u = 0.5. 21 53.67 47.00 (a) Explain why it was important to randomly assign the order in which each subject used the two masks. (b) Do these data provide convincing evidence that the floral scent improved performance, on average? 90. Music and memory Refer to Exercise 88. Which of the following changes would give the test a higher power to detect u = -1: using a = 0.01 or α 0.10? Explain. 87. Growing tomatoes Researchers suspect that Variety A tomato plants have a higher average yield than Variety B tomato plants. To find out, researchers randomly select 10 Variety A and 10 Variety B tomato plants. Then the researchers divide in half each of 10 small 91. Significance and sample size A study with 5000 subjects reported a result that was statistically signifi- cant at the 5% level. Explain why this result might not be particularly large or important. plots of land in different locations. For each plot, a coin toss determines which half of the plot gets a Va- riety A plant; a Variety B plant goes in the other half. After harvest, they compare the yield in pounds for the plants at each location. The 10 differences in yield (Variety A – Variety B) are recorded. A graph of the differences looks roughly symmetric and single-peaked with no outliers. A paired t test on the differences yields t = 1.295 and P-value = 0.1138. 92. Sampling shoppers A marketing consultant observes 50 consecutive shoppers at a supermarket, recording how much each shopper spends in the store. Explain why it would not be wise to use these data to carry out a significance test about the mean amount spent by all shoppers at this supermarket. 93. Do you have ESP? A researcher looking for evidence of extrasensory perception (ESP) tests 500 subjects. Four of these subjects do significantly better (P < 0.01) than random guessing. (a) State appropriate hypotheses for the paired t test. Be sure to define your parameter. (a) Is it proper to conclude that these four people have ESP? Explain your answer. (b) What are the degrees of freedom for the paired t test? (c) Interpret the P-value in context. What conclusion should the researchers draw? (b) What should the researcher now do to test whether any of these four subjects have ESP? 94. Ages of presidents Joe is writing a report on the backgrounds of American presidents. He looks up the ages of all the presidents when they entered office. Because Joe took a statistics course, he uses these numbers to perform a significance test about the mean age makes no sense. (d) Describe a Type I error and a Type II error in this setting. Which mistake could researchers have made based on your answer to part (c)? 88. Music and memory Does listening to music while studying hinder students' learning? Two AP® Sta- tistics students designed an experiment to find out. of all U.S. presidents. Explain why this
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