Statistical Process Control and Capability Analysis

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Statistical Process Control and Capability Analysis Problem 10 - 28 The following is a control chart for the average number of minor errors in 22 service reports. a. Calculate the observed mean, expected mean, standard deviation and z value for the median and up/down test. (Negative amounts should be indicated by a minus sign. Round your answers to 2 decimal places.) Test Observed Expected Std. dev z Median 8.00 ± .05 12.00 ± .05 2.29 ± .05 - 1.75 ± .05 Up/Down 11.00 ± .05 14.33 ± .05 1.89 ± .05 - 1.76 ± .05 b. Based on your calculation conclude whether the test is random or non - random. Test Conclusion Median Random Up/Down Random Explanation: Note that all points are within the control limits, so the process is apparently in control. Run tests: Test Observed Expected Std. dev z Conclusion Median 8.00 12.00 2.29 - 1.75 Random Up/Down 11.00 14.33 1.89 - 1.76 Random Because both the run tests indicated that the output is random, the process is probably random. Problem 10 - 25 An appliance manufacturer wants to contract with a repair shop to handle authorized repairs in Indianapolis. The company has set an acceptable range of repair time of 50 minutes to 90 minutes. Two firms have submitted bids for the work. In test trials, one firm had a mean repair time of 74 minutes with a standard deviation of 4.0 minutes and the other firm had a mean repair time of 72 minutes with a standard deviation of 5.1 minutes. (Do not round intermediate calculations. Round your answers to 2 decimal places.) Firm C pk
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