Question

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

Frequent Quizzes	Two Exams
n = 15	n = 15
M = 72	M = 68

If the first sample variance is s^2=32 and the second sample has s^2=28 , do the data indicate that testing frequency has a significant effect? Again, use a two-tailed test with α=.01.

Choose:

a) Reject the null hypothesis

b) Fail to reject the null hypothesis

Answer 1

Sol:

Ho: 1=2

Ha: 1 2

The test statistic is

t=(xbar1-xbar2)/sqrt(s1^2/n1+s2^2/n2)

=(72-68)/sqrt(32/15+28/15)

t = 2

Given a=0.01, the critical values are t(0.005, df=n1+n2-2=28) =-2.467 or 2.467 (from student t table)

Since t = 2 is between -2.467and 2.467,

we do not reject Ho.

So we can not conclude that testing frequency has a significant effect.

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