7 Johnny Crabcakes wants to compare the average Exam 1 grade

7. Johnny Crabcakes wants to compare the average Exam 1 grades between two classes (sections 102 and 103). But first Johnny has to decide what test he should run in Excel. Use the output in Figure 1 and a.05 significance level to guide Johnny on what the appropriate test is. Note: The output in Figure 1 was generated using a.05 significance level. F-Test Two-sample for variances 103 (n-30)102 (n-35 Mean Variance Observations df 82.16666667 81.14285714 294.2816092 172.1848739 35 34 30 29 1.709102562 0.066982859 1.802003383 p(F | one-tail F Critical one-tall Figure 1: Comparing the variances of Stats II Exam l grades between section 103 and 102 a. Johnny should pool the variances and run an \"equal variance t-test\" b. Johnny should not pool the variances and run an \"unequal variance t-test\" c. Johnny should run a z-test for two proportions d. Johnny should run a t-test for two dependent samples

Solution

7. Since here smaple size are large enough and he wants to compare the mean not variances so Jhony should pool the variances and should run an equal variance t-test. So option a is correct.

8. We are assuming that population variances are not equal so option b is correct.

9.

Criticl value approach:

Since t-stat value (0.593) is less than one tailed critical value(1.321) and test is right tailed so we fail to reject the null hypothesis. That is result is not siginificant.

P-value approach:

Since P value (0.280)-one tailed is greater than 0.10 (level of siginificance) so we fail to reject the null hypothesis. That is result is not siginificant.

Hence, option a is correct.