Arconic Inc. is a producer of aluminum components for the avionics and automotive industries. At its Davenport Works plant, an engineer has conducted a quality-control test in which aluminum coils produced in all three shifts were inspected. The 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?

Transcribed Image Text:

Production Shift Quality First Second Third Good 285 368 176 Defective 15 32 24