An educational psychologist studies the effect of frequent testing on retention

Question

An educational psychologist studies the effect of frequent testing on retention of course material. In one of the professor's sections, students are given quizzes each week. The second section receives only two tests during the semester. At the end of the semester, both sections receive the same final exam, and the scores are summarized below. Do the data indicate that testing frequency had a significant effect on performance? Use a two-tailed test at the .05 level of significance.

   Frequent Quizzes       Two Exams

m1 = 82                             m2 = 78

n1 = 15                               n2 = 15

SS1 = 100                           SS2 = 110

See video lesson for details of computation of independent sample t-test (a bit different from the book)

Submit:

A. Show your computations

B. Complete APA line for the t-test (including effect size - r2)

C. Paragraph answering the research question.

Show your work!

Explanation / Answer

a) Sp = sqrt(/(SS1 + SS2)/(n1 + n2 -2))

= sqrt((100+110)/(82+78-2))

= 1.15287

TS = (M1 -M2)/(Sp*sqrt(1/n1 + 1/n2))

=(82-78)/(1.15287* sqrt(1/78 +1/82))

= 21.93

B critical value for alpha = 0.05 is 1.96

since TS > t-critical

we reject the null and conclude that

the data indicate that testing frequency had a significant effect on performance

effect size =  (M1 -M2)/(Sp)

= (82-78)/(1.15287)

=3.4696

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