In a quality control test of parts manufactured at Dabco Corporation, an engineer sampled parts produced on the first, second, and third shifts. The research study was designed to determine if the population proportion of good parts was the same for all three shifts. Sample data follow.
(A) Using a .05 level of significance, conduct a hypothesis test to determine if the population proportion of good parts is the same for all three shifts.
What is the p-value and what is your conclusion?
(B) If the conclusion is that the population proportions are not all equal, use a multiple comparison procedure to determine how the shifts differ in terms of quality.
What shift or shifts need to improve the quality of parts produced?

Quality first second third
Good 285 368 176
Defective 15 32 24