Assignment 8 Sampling, SPC and Control chart

Transcription

1 Instructions: Assignment 8 Sampling, SPC and Control chart 1. Total No. of Questions: 25. Each question carries one point. 2. All questions are objective type. Only one answer is correct per numbered item. 1. If 5 samples (items) are chosen from a population with defect rate = 0.2, what is the probability that exactly 2 items are defective. a b c d. None of the above 2. In a sampling risk for the producer is 0.2 and the risk for consumer is Identify the probability of acceptance at acceptable quality level (AQL) as well as rejection quality level (RQL). a) 0.2, 0.75 b) 0.8, 0.75 c) 0.2, 0.25 d) 0.8, Larson Nomogram is used to identify a) Sample size (n) b) Control limit (c) d) None of these 4. Smallest numbers of samples are required in a) Single sampling b) Double sampling c) Sequential sampling d) All requires same sample size 5. From a lot of size 2000, a sample of 50 items is taken for inspection. If the probability of accepting a lot is 0.8, Identify average total inspection. a) 50 b) 90 c) 440 d) 10

2 6. Match From a lot size of 1000 items, a sample of 50 items is selected. If the lot comes with the defect level of exactly 0.1 and the probability of accepting the lot is 0.9, identify average outgoing quality a) 0.09 b) 0.9 c) d) The dividing lines between random and non-random deviations from mean of the distribution are known as a) 3-Sigma limits b) Control limits 8. Variation in the dimensions of products coming out of same machine is due to a) Variations by operator b) Improper machine setup c) Process dependency on other environment and system variables d) All of the above 9. The average dimension of outputs of a process does not match with the required one but it s variation is within the acceptance limit. Select the most appropriate option a) Process is accurate but not precise b) Process is precise but not accurate c) Process is neither accurate nor precise 10. A sample is taken out of a lot and inspected, results show that the lot is accurate and precise. 1. The sample mean is same as the required dimension 2. The sample variation is within the acceptable limit 3. All the data points are above and very near to the mean in X bar chart Select the correct option a) Only 1 b) Only 2 c) 1 and 2 d) 1, 2 and 3

3 11. Increasing Two machines produce cylinders of diameter 100 cm. Samples of 10 cylinders have been taken from both the machines, the recorded dimensions are as follows Machine A: {97, 100, 99, 100, 98, 100, 103, 101, 100, 102} Machine B: {98, 101, 100, 101, 99, 101, 104, 102, 101, 103} Select the correct option a) Machine A is more precise than Machine B b) Machine B is more accurate than Machine A c) Machine A and Machine B are equally precise d) Machine A and Machine B are equally accurate 12. Select the correct option a) Control limits are applicable to check the quality of an individual product b) Control limits are applicable to check the quality of a lot 13. Manager X has drawn samples of size 7 items from two different lots of same size. Dimensions recorded out of samples from lot A and lot B are Lot A {50, 51, 53, 48, 54, 47, 52 } Lot B {50, 51, 49, 50, 54, 50, 52 } These two lots are the outcome of two different processes process A and process B. Assume the required dimension is 50. Select the incorrect option a) Process B is more accurate than process A b) Process A is more precise than process B c) Process B is more precise than process A 14. From a lot of size N, few samples of size n are taken and sample means are calculated. Assume the process follows normal distribution. If the standard deviation of the samples of size 100 is 1, what is expected standard deviation of the samples of size 400 a) 0.25 b) 0.5 c) 4 d) High cost, low volume items requires a) Complete inspection b) No inspection c) Random Inspection d) Intensive Inspection 16. Process is In control, if it has a) No variation b) Only natural variations c) Natural as well as Exceptional variations d) b and c

4 17. To check the precession and accuracy of a process we need a) X bar chart b) R chart (Range chart) c) X bar chart as well as R chart d) These two are not sufficient 18. In an experimentation following values have been recorded Average X bar = 200 cm Variation of X bar =1.44 cm Calculate the control limits a) [196.56, ] b) [198.8, 201.2] c) [195.68, ] d) [196.4, 203.6] 19. The In Normal Distribution the area covered between µ ± σ is a) 66 percent b) 95 percent c) 99.7 percent d) 96.6 percent 20. In control charts, upper control limit is a) σ away from the lower control limit b) 2σ away from the lower control limit c) 3σ away from the lower control limit 21. Type 1 error means a) Getting a signal that process is out of control though it is in control b) Getting a signal that process is out of control when it is out of control c) Getting a signal that process is in control though it is out of control d) Getting a signal that process is in control when it is in control 22. In a In an experiment following data have been obtained- Range for the 5 samples ={2,3,4,5,6} UCL factor (D4) = 2 LCL factor (D3) = 0 Find the control limits a) [0, 8] b) [0, 4] c) [0, 16] d) [2, 8]

5 23. In a process following data are recorded Average Range R = 10.0 kg Standard deviation of range = 3.6 Identify the control limits a) [-0.8, 20.8] b) [-0.8, 11.8] c) [0, 20.8] d) [0, 11.8] 24. Process control is carried out a) Before production b) During production c) After production 25. Chart used to monitor attributes is a) R-chart b) Xbar-Chart c) P-chart d) All of the above Answers Key b d c c c c c d b c c b c b d b c d a d a a c b c