APPENDIX D 813 5. The process appears to be within statistical control. However, using the manager’s definition of a defect, the rate of defects is far too high, so corrective action should be taken to lower the service time. Chapter 14: Cumulative Review Exercises 1. a. 0.08 b. 0.17 c. 0.0166 d. 0.729 e. First try to get the case dismissed, then try to arrange for a plea deal. Given the very high conviction rate from trials, a trial should be avoided. 2. 0.440 6 p 6 0.501. Because the confidence interval includes 0.5, we cannot conclude that fewer than half of all adults say that nuclear plants are safe. 3. 47% of 1038 is 488, so 488 of those surveyed said that nuclear plants are safe. H0: p = 0.5. H1: p 6 0.5. Test statistic: z = -1.92. P@value = 0.0272 (Table: 0.0274). Critical value: z = -1.645. Reject H0. There is sufficient evidence to support the claim that fewer than half of all Americans say that nuclear plants are safe. This conclusion does contradict the conclusion from the preceding exercise. Because this hypothesis test is a left-tailed test with a 0.05 level of significance, it is equivalent to a confidence interval with a 90% level of confidence, but the preceding exercise used a 95% level of confidence. 4. Yes. The vertical scale does not begin with 0, so the difference between 47% and 49% is visually exaggerated to give a false impression. 5. r = -0.419. P@value = 0.228 (Table: 70.05). Critical values: r = {0.632. There is not sufficient evidence to support the claim that there is a linear correlation between temperature and carbon dioxide. Even if there had been a linear correlation, that would not be basis for concluding that carbon dioxide causes a rise in temperatures. 6. yn = 16.5 - 0.00412x. The best predicted value of the temperature in the year with a CO2 level of 420 is y = 14.878°C. Because that predicted value is the same for any CO2 level, it is not likely to be accurate. 7. a. 99.89% (Table: 99.88%) b. 0.1587 Chapter 14: Review Exercises 1. x = 3157 kWh, R = 1729 kWh. R chart: LCL = 0 kWh, UCL = 3465 kWh. x chart: LCL = 2322 kWh, UCL = 3992 kWh. 2. The process variation is within statistical control. 3. There appears to be a shift up in the mean values, so the process mean is out of statistical control. 4. There appears to be a slight upward trend. There is 1 point that appears to be exceptionally low. (The author’s power company made an error in recording and reporting the energy consumption for that time period.) The process is not within statistical control.
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