Module 05 Review Questions(1)

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OMBA 6944 Operations and Supply Chain Management Review Questions Module 5 1. In Statistical Process Control, ________ are used to detect defects and determine if the process has deviated from design specifications. A. flowcharts B. cause-and-effect diagrams C. process capability charts D. control charts 2. Which one of the following statements about quality control is true? A. Measurement by attributes is a simple yes or no decision. B. Complete inspection is used when inspection cost is high. C. Sampling inspection is used when the cost of passing a defective unit is high relative to the cost of inspection. D. Measurement by variables is often used when the quality specifications are complex. 3. Which one of the following statements relating to quality is true? A. Sampling procedures based on measurement by variables should be used when quality specifications are complex. B. A distribution of sample means has more variance than the process distribution itself. C. The distribution of sample means can be approximated by the normal distribution. D. Sampling is a better approach than 100 percent inspection when the cost of accepting a defective item is very high. 4. An operator of a filling machine plotted the weights of each bag she filled for three weeks. At the same time, a quality inspector randomly took groups of five bags of the same output and plotted the average weights of the samples. The inspector's sampling distribution will: A. have greater variability than the operator's distribution. B. have less variability than the operator's distribution. C. show if the output has been produced to the operator's specifications. D. have a mean five times greater than the operator's distribution. 5. In SPC, the distribution of sample means: A. can be approximated by the normal distribution.

B. will have greater variability than the process distribution. C. will always have a mean greater than the process distribution because of the sample size. D. cannot be used for control charts because the variability is understated. 6. Regarding control charts, a type II error refers to concluding that the process is: A. in control when it is not in control. B. incapable when it is capable. C. out of control when it is in control. D. capable when it is not capable. 7. An example of a type I error would be: A. throwing away a perfectly good banana. B. counting a student's multiple choice response correct when it is actually incorrect. C. releasing a guilty defendant. D. counting a student's multiple choice response correct when it is actually correct. 8. An example of a type II error would be: A. counting a student's True/False response incorrect when it is actually correct. B. convicting an innocent defendant. C. eating food that you were unaware was spoiled. D. counting a student's True/False response incorrect when it is actually incorrect. 9. Regarding control charts, changing from three-sigma limits to two-sigma limits: A. increases the probability of concluding nothing has changed, when in fact it has. B. increases the probability of searching for an assignable cause when none exists. C. decreases the probability that the process average will change. D. decreases the probability that defects will be generated by the process. 10. Regarding control charts, changing from two-sigma limits to three-sigma limits: A. increases the probability of concluding nothing has changed, when in fact it has. B. increases the probability of searching for a cause when none exists. C. decreases the probability that the process average will change. D. decreases the probability that defects will be generated by the process. 11. The UCL and LCL for an x-bar chart are 50 and 40 respectively. The central line is 45, and the process variability is considered to be in statistical control. The results of the next six sample means are 48, 43, 47, 41, 54, and 46. What should you do? A. Nothing; the process is in control. B. Explore the assignable causes because at least one of the sample means is outside the control limits.

C. Explore the assignable causes because there is a run. D. Explore the assignable causes because there is a trend. 12. The underlying statistical distribution for the p-chart is: A. Poisson. B. binomial C. percentage. D. normal. 13. Jars of pickles are sampled and weighed. Sample measures are plotted on control charts. The ideal weight should be precisely 11 oz. Which type of chart(s) would you recommend? A. p -chart B. c -chart C. both an x -bar chart and an R -chart D. an x -bar chart, but not an R -chart E. both a p -chart and a c -chart 14. The usual purpose of an R-chart is to signal whether there has been a: A. gain or loss in dispersion. B. change in the percent defective in a sample. C. change in the central tendency of the process output. D. change in the number of defects in a sample. E. change in the consumer's risk. 15. To set x -bar chart upper and lower control limits, one must know the process central line, which is the: A. average of the sample means. B. total number of defects in the population. C. percent defects in the population. D. size of the population. E. average range. 16. A pizza store is interested in monitoring the proportion of pizzas that are delivered late to its customers. An appropriate control chart would be: A. an x-bar chart. B. a p-chart. C. a c-chart. D. an R-chart.

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17. A company is interested in monitoring the number of scratches on Plexiglass panels. The appropriate control chart to use would be: A. an x-bar chart. B. a p-chart. C. a c-chart. D. an R-chart. 18. The normal application of a p -chart is in: A. process sampling by variables. B. acceptance sampling by variables. C. process sampling by attributes. D. acceptance sampling by attributes. E. process capability ratio computations. 19. What is the statistical process chart used to control the number of defects per unit of output? A. x -bar chart B. R -chart C. p -chart D. AOQ chart E. c -chart 20. The local newspaper receives several complaints per day about typographic errors. Over a seven-day period, the publisher has received calls from readers reporting the following total daily number of errors: 4, 3, 2, 6, 7, 3, and 9. Based on these data alone, what type of control chart(s) should the publisher use? A. p -chart B. c -chart C. x -bar chart D. R -chart E. x -bar chart and R -chart 21. Which alternative will increase the probability of detecting a shift in the process average? A. increasing the control limit spread B. taking smaller samples C. taking smaller samples more frequently D. taking larger samples more frequently 22. Four samples of size 5 were taken from a process. A range chart was developed that had LCL R = 0 and UCL R = 5.50. Similarly, an average chart was developed using the measurements from the five samples, with LCL = 25.0 and UCL = 40.0. The ranges for

each of the five samples were 3.75, 2.42, 4.75, 2.04, and 5.80, respectively. The values of the sample average for each sample were 29.5, 27.3, 27.4, 26.1, and 28.9, respectively. What can you tell management from this analysis? A. The process average is out of control. B. The process variability is out of control. C. Both the process variability and the process average are out of control. D. We cannot tell if the process variability or the process average is out of control. 23. Historically, the average time to serve customers at a restaurant fast food window has been 4 minutes and the standard deviation has been 0.75 minutes. Management would like to specify the control limits for an chart with a size of sample n=8 and a normal deviate of 3 standard deviations from the mean. The LCL for the chart would be: A. less than 2. B. greater than 2 but less than or equal to 3. C. greater than 3 but less than or equal to 4. D. greater than 4. 24. Historically, the average time to serve customers at a restaurant fast food window has been 4 minutes and the standard deviation has been 0.75 minutes. Management would like to specify the control limits for an chart with a size of sample n=8 and a normal deviate of 3 standard deviations from the mean. The UCL for the chart would be: A. less than 3. B. greater than 3 but less than or equal to 4. C. greater than 4 but less than or equal to 5. D. greater than 5. 25. Historically, the average time to serve customers at a restaurant fast food window has been 4 minutes and the standard deviation has been 0.75 minutes. Management would like to specify the control limits for an chart with a size of sample n=8 and a normal deviate of 3 standard deviations from the mean. Suppose the average service time from the next 6 samples yielded the following result: 3.2, 2.1, 5.6, 4.8, 3.9, 5.5 minutes. What conclusion can be drawn? A. Assuming the process variability is in control, the process average is also in statistical control. B. Assuming the process variability is in control, the process average is out of statistical control. C. The sample size should be increased. D. No conclusion can be drawn because there is insufficient data. 26. The consultant suspiciously eyed the c-chart that Chickenverks used to monitor the number of broken eggs in each 100 egg carton. "You know you really should be using a p-chart," the consultant commented with an air of superiority. "What's the difference between a p-chart and a

c-chart in this application?" the long time Chickenverks employee asked with an obvious edge to his voice. "Well," the consultant replied, "the difference is: A. the width of the three sigma limits for the c-chart is 100 times greater than those of the p- chart." B. the three-sigma p-chart will catch problems earlier than the three sigma c-chart." C. the three-sigma c-chart will catch problems earlier than the three sigma p-chart." D. well, OK, you got me. The charts will look and behave the same for all practical purposes." 27. Process capability can be addressed when: A. assignable causes are present. B. a process is in statistical control. C. a process is in statistical control but assignable causes are present. D. the nominal value equals the tolerance regardless of assignable causes. 28. The manager at a pizza store has a target value of 20 minutes for the delivery of pizzas. The delivery team consistently averages 19.8 minutes with a standard deviation of 0.5 minutes. Based on customer feedback, the manager has established upper specification limit of 22 minutes and a lower specification limit of 18 minutes for pizza deliveries. Which statement concerning this process is true? A. The process capability ratio is 1.46. B. The process capability index is 1.33. C. The process is in control. D. None of these is true. 29. The manager at a pizza store has a target value of 20 minutes for the delivery of pizzas. The delivery team consistently averages 19.8 minutes with a standard deviation of 0.5 minutes. Based on customer feedback, the manager has established upper specification limit of 22 minutes and a lower specification limit of 18 minutes for pizza deliveries. What is the process capability index? A. 1.20 B. 1.33 C. 1.46 D. 1.66 30. MKS Inc., produces meter sticks that have a target length of 100 centimeters with upper and lower specification limits of 100.05 and 99.95 centimeters respectively. They are considering the purchase of a new machine that can hold a process output average exactly to target with a standard deviation of 0.02. Which would their process capability index be if they splurged and purchased the new machine? A. 0.44 B. 0.83

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C. 1.26 D. 1.78 31. A manufacturer embarking on a Six Sigma program sets the goal of having true Six Sigma capability for all processes by the end of the month. If their current process capability index on a key metric is less than 2.0 and the process capability ratio is 1.0, what must happen with the process standard deviation? A. The process standard deviation must be doubled. B. The process standard deviation must be reduced by a factor of six. C. The process standard deviation must be cut in half. D. The process tolerances should be doubled.

Module 05 Review Questions(1)

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