Question

Help finding critical value.

A) A company found that 27 out of 150 of its products were defective after retraining its employees. If the company normally has a 40% defective product rate, find the critical value to determine if retraining the employees helped to minimize the number of defective products.

B) A teacher gives 200 students a study guide for a test and the average score was 90 with a standard deviation of 6. She did not give the other 200 students a study guide and their average score was 70 with a standard deviation of 8. Find the critical value to determine whether or not the study guide helped students to increase their test score.

Here is my work. I am being told these are incorrect. Where am I going wrong?

우리 ->pa 二1.649 200 + 200 = 400-2 =398 19,--21/15° .10 4(lay)÷150

Answer 1

a) H₀: P = 0.4

    H₁: P < 0.4

At alpha = 0.05, the critical value is z_0.025 = -1.96

b) H₀: $\mu 1 = \mu 2$

    H₁: $\mu 1 > \mu 2$

At alpha = 0.05, the critical value is z_0.025 = 1.96