A teacher gives a reading skills test to a third-grade class of n=25 students at

Question

A teacher gives a reading skills test to a third-grade class of n=25 students at the beginning of the school year. To evaluate the changes that occur during the year, students are tested again at the end of the year. Their test scores showed an average improvement of M_o = 12.7 with s^2 = 100. Are the results sufficient to conclude that there is significant improvement? Use a one tail test with =.01 Construct a 90% confidence interval for the mean difference to describe the size of the improvement.

Explanation / Answer

t = 12.7 / srqt ( 100 / 25 )

t = 6.35

for alpha = 0.01 df = 99 critical value : 2.358

since t > critical value we conclude that there is significnat improvement

b)

alpha / 2 = 0.05   df = 99    t= 1.662

I: 12.7 +/- 1.662 * srqt ( 100 / 25 )

12.7 +/- 3.324

9.376 < miu < 16.024

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