A Quality Control Engineer Is in Charge of the Manufacture

Multiple Choice

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) Friedman rank test
C) Z test for difference in proportions
D) ç² test for difference in proportions