Question 946:

Asked on April 29, 2012

Tags: 2-sample t-test

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1. Q946_1_q946.xls

We want to test the hypothesis that the absenteeism differs based on the work week.  The Null Hypothesis is that the mean hours absent are the same between groups. The alternative hypothesis is that the mean absent hours differ. We will reject the Null Hypothesis if we have evidence at the .05 level. We will conduct a 2-sample t-test.

1. First we create the test statistic t which is the difference between means divided by the pooled standard deviations (see the calculator for the somewhat tedious calculations). We get .4/.2915 = 1.3719
2. We now look up this test statistic using a t-table with 78 degrees of freedom. The attached excel file uses a formula to look it up for you. This generates a p-value of .174
3. Because the p-value of .174 is GREATER than .05 we fail to reject the Null Hypothesis.
4. There is insufficient evidence to conclude the mean absent hours differ.