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C291FE2012_FinalVersion_Apr9

B suppose that the same data have come from a

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b) Suppose that the same data have come from a differently designed experiment where 20 cars were used; 10 were shown to Appraiser 1 and the other 10 to Appraiser 2. Car 1 2 3 4 5 6 7 8 9 10 Appraiser 1 1650 360 660 1050 890 750 470 1270 550 730 Car 11 12 13 14 15 16 17 18 19 20 Appraiser 2 1440 380 600 920 930 650 410 1080 480 770 Which output is the more appropriate? (Circle your choice) OUTPUT 1 OUTPUT 2 State your conclusion, clearly, in one sentence. (Note: You still don’t have to do any computations; just use the results from the output you selected.) c) Construct a 95% confidence interval for the difference in mean appraisals between the two appraisers. Use the formula based on the pooled standard deviation; to simplify your calculations, we have computed it for you: s p = 361. Report your answer to the nearest whole numbers, with the format (xxx , xxx). 10
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Question 6. (Total 9 marks) “RVs about RVs!” A manufacturing plant for recreational vehicles receives shipments from three different parts vendors. There has been a defect issue with some of the electrical wiring in the recreational vehicles manufactured at the plant. The plant manager believes that the defect issue is dependent on the parts vendor. The plant manager reviews a sample of quality assurance inspections from the last six months. Vendor Inspection Result Perfect Parts Co. Made-4-U Co. 25 Hour Parts Co. Unacceptable 54 48 70 Perfect 94 72 88 Not perfect but acceptable 22 30 22 a) What is the probability that a randomly selected shipment is Unacceptable? __ A. 0.108 __ B. 0.314 __ C. 0.318 __ D. 0.344 __ E. 0.686 b) What is the probability that a randomly selected shipment is Unacceptable given that it came from the Perfect Parts Co. __ A. 0.108 __ B. 0.314 __ C. 0.318 __ D. 0.344 __ E. 0.686 c) Which of the following statements are correct to use as an appropriate null hypothesis for a chi-square test based on these data? Check as many as apply. __ (1) Inspection result and vendor are dependent. __ (2) The proportions of each inspection result are independent of vendor. __ (3) The distribution of inspection results is the same for all three vendors. d) Compute the expected frequency and the contribution to the chi-square statistic that comes from the top-left cell ( Unacceptable and Perfect Parts Co. )? Report each to two decimal places. Expected Frequency = ______ Chi-square term = ________ e) What are the degrees of freedom for the chi-squared statistic in this situation? ____ f) The chi-squared stat for this table is 6.63. In what range is the corresponding P -value? __ A. P -value < 0.005 __ B. 0.005 < P -value < 0.01 __ C. 0.01 < P -value < 0.025 __ D. 0.025 < P -value < 0.05 __ E. P -value > 0.05 g) At the 5% significance level, which of the following is a correct conclusion? __ A. Reject the null hypothesis. __ B. There is a significant association between inspection results and vendor. __ C. Inspection results and vendor are correlated. __ D. There is insufficient evidence of an association between inspection results 11
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and vendor. 12
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Question 7. (Total 15 marks) “Making progress from process” An operations manager wanted to determine if there is a relationship between the amount of training received by production line workers and the time it takes for them to trouble shoot a process problem. For a random sample of recently trained line workers, the number of hours of training time received and the time it took (in minutes) for them to troubleshoot their last process problem were recorded. The data and some of the Excel
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