An English teacher has been teaching a sixth grade composition class for many years. He has the feeling that over the past several years, the writing ability of students has changed. A national test of proficiency in composition was administered 5 years ago. The resulting distribution of scores was normally shaped, had a mean of 85 and a standard deviation of 10.9. In order to test his feeling, he gives his present class of 43 students the same proficiency test. The resulting mean is 80 and the standard deviation is 8.7. Using the z test with a = 0.05 2 tail , the appropriate critical value is _________.
A) z crit = - 1.645
B) z crit = ±1.96
C) z crit = - 1.96
D) z crit = ± 1.645

Question

Quizplus · Accepted Answer

For a two-tailed test with an alpha level of 0.05, the critical z values are ±1.96. This divides the tail of the normal distribution into two parts, each containing 2.5% of the total area (or probability).

An English Teacher Has Been Teaching a Sixth Grade Composition