LOYOLA COLLEGE (AUTONOMOUS), CHENNAI – 600 034

M.Sc. DEGREE EXAMINATION – STATISTICS

AC 46

FOURTH SEMESTER – APRIL 2006

                                                     ST 4801 – INDUSTRIAL STATISTICS

 

 

Date & Time : 25-04-2006/9.00-12.00         Dept. No.                                                       Max. : 100 Marks

 

 

PART – A

Answer all the questions.                                                                                  10 ´ 2 = 20

1. Discuss the logic and statistical basis underling the general use of 3 – sigma limits on control charts.
2. Mention the theoretical basis of p – chart and set up its control limits.
3. How is lack of control of a process determined using control chart techniques?
4. What is process capability ratio (PCR)?
5. Write down the control limits of a coefficient of variation chart.
6. What is an average run length (ARL)?
7. Explain an attribute single sampling plan.
8. Define AOQ for a single sampling plan.
9. Discuss the concepts of chance and assignable causes of variability.
10. Write a short note on multivariate control chart.

 

PART – B

Answer any five questions.                                                                     5 ´ 8 = 40

 

11. Explain the method of constructing control limits for X-bar and R charts when the sample sizes are different for various subgroups.
12. A control chart indicates that the current process fraction non-conforming is 0.02. If 50 samples are inspected each day, what is the probability of detecting a shift in the fraction non-conforming to 0.04 on the first day after shift? By the end of the third day following the shift?
13. Write a detail note on the moving average control chart.
14. Consider a modified control chart with CL at m = 0 and s =1. If n = 5, the tolerable fraction non-conforming d = 0.00135 and the control limits are at 3, sketch the OC curve of the chart.
15. Design a cumulative sum control chart to detect a shift of D = 0.75 that has L(0) = 400. Is it possible to find a cumulative sum control chart for detecting this shift that has L(0.75) £ 12? What is L(0) for this chart?
16. For the double sampling plan N = 120, n₁ = n₂ = 13, c₁ =0 and c₂ = 1, obtain P_a, ASN, AOQ and ATI when the submitted lot has the fraction non – conforming at p = 0.18.
17. What are acceptances and rejection lines of a sequential sampling plan for attributes? How are the OC and ASN values obtained for this plan?
18. What are modified control charts? Explain the method of obtaining control limits.

 

PART – C

Answer any two questions.                                                                   2 ´ 20 = 40

 

19. a). Distinguish between c and u charts. Explain the situations where c and u charts are

applicable and how are the limits obtained for these charts.

b). Explain the procedure of obtaining the OC curve for a p – chart with an

illustration.

(10 + 10)

20. a). Define the terms i). Rational subgroups ii). Specification limits

iii). Natural tolerance limits iv). Probability limits.

b). Explain the relevance of non-parametric method in quality control procedures with

an illustration.                                                                                              (10 + 10)

21. a). What purpose does a cumulative sum chart serve?

b). Outline the procedure of constructing a V-mask.                                         (5 + 15)

22. a). What are continuous sampling plans and mention a few situation where these

plans are applied

b). Explain with an illustration the method of obtaining the probability of acceptance

for a triple sampling plan.                                                                            (10 + 10)

 

 

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