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)$\chi$ ² test for difference in proportions. D)Kruskal-Wallis rank Test.

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Quizplus · Accepted Answer

We will use a Z test for difference in proportions to compare the two manufacturing methods because we are comparing two independent groups with a dichotomous outcome (defective or not defective). A paired t test would be used if the same group was measured twice (before and after a treatment or with two different methods). The Kruskal-Wallis rank test is used to compare three or more groups with nonparametric data. The chi-square test for difference in proportions is used for categorical data with more than two groups.

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