Download AP Stats HW 10.3b

1
Exercises
Right versus left The design of controls and instruments affects how easily people can use them. A
student project investigated this effect by asking 25
right-handed students to turn a knob (with their
right hands) that moved an indicator. There were
two identical instruments, one with a right-hand
thread (the knob turns clockwise) and the other with
a left-hand thread (the knob must be turned counterclockwise). Each of the 25 students used both •
instruments in a random order. The following table
gives the times in seconds each subject took to move
the indicator a fixed distance:30
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Subject
RignTthread
Leffthread
1 .
113
137
2
105
3
130
133
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4
101
108
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5
138
115
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6
118
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87
103
8
116
145
9
75
78
10
96
107
84
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13
116
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14
107
87
15
118
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123
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135
19
111
88
78
101
123
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147
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100
89
85
76
116
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(a) Explain why it was important to randomly assign
the order in which each subject used the two knobs.
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(b) The project designers hoped to show thatrigKFn
handed people find right-hand threads easier to use.
Carry out a significance test at the 5% significance
level to investigate this claim.
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94. Significance and sample size A study with 5000
subjects reported a result that was statistically significant at the 5% level. Explain why this result might ._
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not be particularly large or important.
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95 Sampling shoppers A marketing consultant
observes 50 consecutive shcippers at a supermarket,
recording how much each shopper spends in the
store Explain why it would not be wise to use these
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96. 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 of all U.S. presidents. Explain why this
makes no sense.
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97. Do you have ESP? A researcher looking for
evidence of extrasensory perception (ESP) tests
500 subjects. Four of these subjects do significantly
better (P< 0.0 1) than random guessing.
(a) Is it proper to conclude that these four people
have ESP? Explain your answer.
(b) What should the researcher now do to test
whether any of these four subjects have ESP?
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