(Two-Sample t-Test Assuming Unequal Variances)

1. Refer to Example 10.21. If the ratio of the two sample variances had been so large that you could not assume equal variances (we use “greater than 3” as a rule of thumb), you should select Stat ➤ Basic Statistics ➤ 2-Sample t, but Do NOT check the box marked “Assume Equal Variances.” If we use this test on the data from Example 10.17, the following output results (Figure 10.27).

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Session Two-Sample T-Test and Cl: Teacher A, Teacher B Method i mean of Teacher A mean of Teacher Difference: Descriptive Statistics Sample N Mean StDev SE Mean Teacher A 8 81.63 9.91 3.5 Teacher 9 1.78 8.80 2.9 Estimation for Difference 95% C for Difference Difference Test -0.15 (-9.95.9.65) H-0 Null hypothesis Alternative hypothesis M T-Value DF P-value -0.03 14 0.974