Question: A weight-loss program guarantees, "You'll lose weight within two weeks or we'll refund your money plus $10!" Using α = 5%, perform the sign test of the median paired difference to determine whether the median weight of these twelve participants decreased.
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Weight
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Weight
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Person
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Before
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After
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Ann
|
150
|
152
|
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Bob
|
213
|
214
|
|
|
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Chris
|
249
|
238
|
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Debby
|
114
|
115
|
|
|
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Earl
|
144
|
144
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|
|
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Fred
|
132
|
133
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|
|
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Gary
|
187
|
188
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|
|
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Helen
|
163
|
164
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|
|
|
Ira
|
210
|
204
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|
|
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Jessie
|
195
|
196
|
|
|
|
Kim
|
124
|
125
|
|
|
|
Linda
|
228
|
229
|
|
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In a two-tailed sign test the observed value of the test statistic is the number of the less frequent sign: the smaller of n (+) the number of +'s or n (-) the number of -'s.
IN A ONE-TAILED SIGN TEST the test statistic may be n (+) or n (-), DEPENDING ON WHICH WAY YOU SUBTRACT!