An educational psychologist studies the effect of frequent testing on retention of class material. In one...

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An educational psychologist studies the effect of frequenttesting on retention of class material. In one section of anintroductory course, students are given quizzes each week. A secondsection of the same course receives only two tests during thesemester. At the end of the semester, both sections receive thesame final exam, and the scores are summarized below.
Frequent Quizzes Two Exams
n=20 n=20
M=73 M=68
a. If the first sample variance is s2 = 38 and the second samplehas s2 = 42, do the data indicate that testing frequency has asignificant effect on performance? Use a two-tailed test at the .05level of significance. (Note: because the two sample are the samesize, the pooled variance is simply the average of the two samplevariances.)
b. If the first sample variance is s2 = 84 and the second samplehas s2= 96, do the data indicate that testing frequency has asignificant effect? Again, use a two-tailed test with x = .05.
c. Describe how the size of the variance effects the outcome ofthe hypothesis test.

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SolutionaState the hypotheses The first step is tostate the null hypothesis and an alternative hypothesisNull hypothesis u1 u 2Alternative hypothesis u1 u 2Note that these hypotheses constitute a twotailed test Thenull hypothesis will be rejected if the difference between samplemeans is too big or if it is too smallFormulate an analysis plan For this analysisthe significance level is 005 Using sample data we will conducta twosample ttest of the null hypothesisAnalyze sample data Using sample data wecompute the standard error SE degrees of freedom DF and the tstatistic See Answer

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