A quality control engineer is in charge of the manufacture of computer disks. Two different processes can be used to manufacture the disks. He suspects that the Kohler method produces a greater proportion of defects than the Russell method. He samples 150 of the Kohler and 200 of the Russell disks and finds that 27 and 18 of them, respectively, are defective. If Kohler is designated as "Group 1" and Russell is designated as "Group 2," which of the following tests will you use to find out if the Kohler method is worse than the Russell method? A) paired t test B) Z test for difference in proportions C) χ² test for difference in proportions D) McNemar test

Question

Quizplus · Accepted Answer

The appropriate test to compare the proportions of two independent groups is the Z test for difference in proportions. The other options are not appropriate for this scenario: 
A) Paired t-test is used to compare paired observations, which is not the case here.
C) χ² test for difference in proportions is used for comparing more than two groups, which is not the case here. 
D) McNemar test is used for comparing proportion of dependent groups, which is not the case here.

A Quality Control Engineer Is in Charge of the Manufacture