Quality_Control_In-Class_Problems - c Suppose samples of...

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Quality Control Problems 1. A firm wishes to set up Mean and Range charts for lathes producing steel shafts of diameter 2 inches. Five samples are taken, each of size 4, and the diameters are measured. Sample Observation 1 2 3 4 1 1.96 2.01 2.04 1.97 2 2.05 2.02 1.93 1.99 3 1.98 1.95 2.02 2.05 4 2.03 1.98 1.97 2.00 5 1.9 2.01 1.97 2.04 a. Find the appropriate control limits. b. After the control limits have been established, a sample of size 4 is taken and inspected. The diameters are as follows: 1.92, 1.97, 2.08, 1.95 inches. Does the process appear to be in control? 2. A process producing TV tubes has an average yield of 90%, based on 20 samples. Samples taken for inspection have a size of 25. a. Set up 2 sigma control limits for the mean proportion defective. b. How can we obtain tighter control limits?
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Unformatted text preview: c. Suppose samples of size 100 are taken. What are the new control limits? d. Three samples, each of size 100, are taken; the numbers defective are 8, 13, and 3. Is the process in control? What action, if any, should be taken? 3. An apparel manufacturer wishes to set up 3 sigma control limits for the shirt making process. Each shirt has an average of 1 defect. What are the appropriate control limits for the process? 4. A semiconductor is designed to have a life of 1000 ± 50 hours. The manufacturing process produces semiconductors with a mean life of 980 hours and a standard deviation of life of 15 hours. Is the process capable of meeting design specifications? What are your recommendations?...
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