The coded values for a measure of brightness in paper (light reflectivity), prepared by two different processes, are as shown in the accompanying table for samples of size 9 drawn randomly from each of the two processes. Do the data present sufficient evidence to indicate a difference in locations of brightness measurements for the two processes? Give the attained significance level.
A B
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6.1
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9.1
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9.2
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8.2
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8.7
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8.6
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8.9
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6.9
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7.6
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7.5
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7.1
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7.9
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9.5
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8.3
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8.3
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7.8
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9.0
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8.9
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a Use the Mann-Whitney U test.
b Use Student's t test.
c Give specific null and alternative hypotheses, along with any assumptions, for the tests used in parts (a) and (b).