Question 136326
The e-mail usage for two different plants of a large company was compared at level of significance 0.05. Samples of ten employees were selected at each plant.
 The mean number of e-mail messages sent per employee for one plant was 15.5 per week and the standard deviation was 5.0. 
For the other plant, the mean was 18.4 and the standard deviation was 1.6.
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For the test of equal population means (assuming equal population variances), the degrees of freedom, the absolute value of the computed test statistic, and the critical values for the test statistic respectively are:
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I ran a 2-Sample T-test on a TI calculator to find
df=18, test stat of -1.74686..., 
Critical values for a 2-tail T-test with df=18 are
+-2.101 for alpha=5%.
Answer: A
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Cheers,
Stan H.
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a. 18, 1.75, ± 2.101
b. 11, 1.75, ± 2.201
c. 18, 1.75, ± 1.96
d. 11, 2.201, ± 1.75
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