Each day at a large hospital, several hundred laboratory tests are performed. The rate at which these tests ate done im properly (and therefore need to be redone) seems steady, at I about 4%. In an effort to get to the root cause of these non conformances, tests that need to be redone, the director of the lab decided to keep records over a period of one week. The laboratory tests were subdivided by the shift of workers who performed the lab tests. The results are as follows:
LAB ThSTS PERFORMED Day Evening Total
SHIFT
Nonconforming 16 24 40 Conforming 654 306 960 Total 670 330 1,000
a. Construct contingency tables based on total percentages, row percentages, and column percentages. b. Which type of percentage—row, column, or total—do you think is most informative for these data? Explain. c. What conclusions concerning the pattern of nonconform ing laboratory tests can the laboratory director reach?
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