operation management 1

1. What do the sequencing rules SPT, DDATE, and SLACK mean? 2. What is the advantage of the SPT rule? Of the DDATE rule? 3. According to Garvin, what are at least 8 different types of design quality? 4. What are four types of quality costs? Give examples of each. 5. Who is the most well-known quality "guru" whose ideas got major exposure in Japan? 6. What are the seven tools of continuous improvement? 7. What are two types of breakthrough improvement? 8. For what purposes are control charts used? 9. If acceptance sampling is used, what happens if the number of defects found in a sample exceeds the allowable number of defects? 10. Give an example of an attribute measurement and a variable measurement. 11. Give an example of a single-channel, single phase service system, a single-channel, multiple-phase service system, and a multiple-channel, single-phase service system. 12. What are the assumptions of the basic mathematical queuing models? Why must the arrival rate be less than the service rate? 13. Define critical path. 14. How is the earliest start time for an activity calculated? The latest finish time? Problems 15. Using the shortest processing time rule, what is the sequence in which the jobs should be performed? a) A B C D E b) A C B D E c) A C B E D d) E B A C D 16. What is the average flow time using SPT? a) less than or equal to 10 days b) greater than 10, but less than or equal to 11 days c) greater than 11, but less than or equal to 12 days d) greater than 12 days 17. Using the DDATE rule, what is the average lateness? a) less than or equal to 3 days b) greater than 3, but less than or equal to 4 days c) greater than 4, but less than or equal to 5 days d) greater than 5 days Job Processing Time (days) Due Date A 1 6 B 4 8 C 3 5 D 5 10 E 7 9 Alice’s Stain Glass Design produces 80 stained glass windows per day. The percentage of windows that come out perfectly the first time average 70% and the percentage of defective stained glass windows that can be reworked is 33 1/3%. The direct manufacturing cost is $200 per window. Rework costs $100 per window. 18. What is the yield for Alice’s Stain Glass Design? a) 56 b) 64 c) 18 d) 22 2/3 e) none of the above 19. What is Alice’s manufacturing cost per window after taking rework into consideration? a) $300 b) $233.33 c) $262.50 d) $140 e) none of the above 20. What is Alice’s new daily product yield if product quality is increased by 10%? a) 77 b) 64 c) 69 d) 72 e) none of the above 21. Peretti Manufacturing produces 32,000 units per month, 75% of which are free of defects. The percentage of defective units which can be reworked is 25%. What is the product yield for Peretti Manufacturing? a) 26,000 b) 24,000 c) 32,000 d) 28,500 e) none of the above 22. Peretti is investigating a new process that will not allow any rework. If the yield through the first process is 90%, the yield through the second process is 92%, and the yield through the third process is 95%, how many units will be produced each month if 32,000 are started? a) 32,000 b) 28,800 c) 25,171 d) 22,000 e) none of the above 23. If Peretti needs 32,000 units to be finished each month, how many units must be started each week with the new process to yield 32,000? a) 40,681 b) 50,000 c) 35,555 d) 28,800 e) none of the above 24. A sample of 50 knit hats was picked from each of 150 cartons of a ski manufacturer’s product. The average proportion of defective hats in each sample was found to be 0.01. What are the control limits for the p-chart? a) LCL = 0.0 UCL = 0.04232 b) LCL = 0.0 UCL = 0.05232 c) LCL = -0.004107 UCL = 0.014107 d) LCL = -0.03222 UCL = 0.04232 You may need the following table to complete the next problems: Table 1 Factors for Determining Control Limits 25. Four samples of size five were taken from a process. The average of the range value was .1625. The average of the sample means was .7275. Using the ! -chart together with an R-chart, what are the control limits for the ! -chart? a) LCL = 0 UCL = .822 b) LCL = .565 UCL = .890 c) LCL = .4025 UCL = 1.0525 d) LCL = .633 UCL = .822 e) none of the above 26. A single-server queuing system has an arrival rate 4 per hour and the average service time is 12 minutes. Which of the following statements is true? a) the average number of units in the waiting line is 1.5 b) the average time a customer spends waiting in line is 48 minutes c) the probability the server is busy is .20 d) the average time a customer spends in the system is .125 hours e) more than one statement above is true 27. 5 B D 4 4 A 6 F 3 3 5 C E 6. Sample size A2 D3 D4 2 1.88 0 3.27 3 1.02 0 2.57 4 0.73 0 2.28 5 0.58 0 2.11 6 0.48 0 2.00 7 0.42 0.88 1.92 8 0.37 0.14 1.86 9 0.34 0.18 1.82 10 0.31 0.22 1.78 x x a. Show early start, early finish, and late start, late finish dates on the appropriate line (10 pts). b. Which activities are on the critical path (2 pts.)? c. Show much slack is in activity B-D (1 pt.)? Formulas For the Single-Server Model Probability that no customers are in the system: Probability of exactly n customers in the system: Average number of customers in the system: Average number of customers in waiting line: Average time a customer spends in the system: Average time a customer spends waiting in line to be served: Lq = ? µ(µ - ?) 2 Pn = P0 ? µ ? ? ? ? ? ? n W = ! 1 µ - ? L = ! ? µ - ? P0 = 1- ? ? ? ? ? ? ? µ Wq = ? µ(µ - ?)