# Statistical Quality Control-Control Charts (ISS (Statistical Services) Statistics Paper IV): Questions 15 - 16 of 31

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## Question number: 15

» Statistical Quality Control » Control Charts » Variable

Essay Question▾

### Describe in Detail

A electric Company uses a process to paint refrigerators with a coat of enamel. During each shift, a sample of five refrigerators is selected and the thickness of the paint in mm is determined. Find upper control limit (UCL) the lower control limit (LCL) for chart.

 Sample No. Observations 1 2.7 2.3 2.6 2.4 2.7 2 2.6 2.4 2.6 2.3 2.8 3 2.3 2.3 2.4 2.5 2.4 4 2.8 2.3 2.4 2.6 2.7 5 2.6 2.5 2.6 2.1 2.8 6 2.2 2.3 2.7 2.2 2.6 7 2.2 2.6 2.4 2.0 2.3 8 2.8 2.6 2.6 2.7 2.5 9 2.4 2.8 2.4 2.2 2.3 10 2.6 2.3 2.0 2.5 2.4 11 3.1 3.0 3.5 2.8 3.0 12 2.4 2.8 2.2 2.9 2.5 13 2.1 3.2 2.5 2.6 2.8 14 2.2 2.8 2.1 2.2 2.4 15 2.4 3.0 2.5 2.5 2.0 16 3.1 2.6 2.6 2.8 2.1 17 2.9 2.4 2.9 1.3 1.8 18 1.9 1.6 2.6 3.3 3.3 19 2.3 2.6 2.7 2.8 3.2 20 1.8 2.8 2.3 2.0 2.9

### Explanation

 Sample No. Observations Total Sample Mean () Sample Range (R) 1 2.7 2.3 2.6 2.4 2.7 12.70 2.54 0.40 2 2.6 2.4 2.6 2.3 2.8 12.70 2.54 0.50 3 2.3 2.3 2.4 2.5 2.4 11.90 2.38 0.20 4 2.8 2.3 2.4 2.6 2.7 12.80 2.56 0.50 5 2.6 2.5 2.6 2.1 2.8 12.60 2.52 0.70 6 2.2 2.3 2.7 2.2 2.6 12.00 2.40 0.50 7 2.2 2.6 2.4 2.0 2.3 11.50 2.30 0.60 8 2.8 2.6 2.6 2.7 2.5 13.20 2.64 0.30 9 2.4 2.8 2.4 2.2 2.3 12.10 2.42 0.60 10 2.6 2.3 2.0 2.5 2.4 11.80 2.36 0.60 11 3.1 3.0 3.5 2.8 3.0 15.40 3.08 0.70 12 2.4 2.8 2.2 2.9 2.5 12.80 2.56 0.70 13 2.1 3.2 2.5 2.6 2.8 13.20 2.64 1.10 14 2.2 2.8 2.1 2.2 2.4 11.70 2.34 0.70 15 2.4 3.0 2.5 2.5 2.0 12.40 2.48 1.00 16 3.1 2.6 2.6 2.8 2.1 13.20 2.64 1.00 17 2.9 2.4 2.9 1.3 1.8 11.30 2.26 1.60 18 1.9 1.6 2.6 3.3 3.3 12.70 2.54 1.70 19 2.3 2.6 2.7 2.8 3.2 13.60 2.72 0.90 20 1.8 2.8 2.3 2.0 2.9 11.80 2.36 1.10 Total 50.28 15.40

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## Question number: 16

» Statistical Quality Control » Control Charts » Variable

Essay Question▾

### Describe in Detail

A machine is manufacturing mica discs. Samples of size 5 are drawn every hour and their thickness in units are recorded as follows. On the basis of chart, Check whether the production is under control?

 Sample No. Observations 1 8 9 15 4 11 2 7 10 7 6 8 3 11 12 10 9 10 4 12 8 6 9 12 5 11 10 6 14 11 6 7 7 10 4 11 7 10 7 4 10 10 8 8 11 11 7 7 9 8 11 8 14 12 10 12 9 12 17 11 11 7 7 9 17 13 12 9 9 4 4 11 13 10 12 12 12 12 14 8 11 9 6 8 15 10 13 9 4 9 16 9 11 8 5 11

### Explanation

 Sample No. Observations Total Sample Mean Sample Range 1 8 9 15 4 11 47 9.4 11 2 7 10 7 6 8 38 7.6 4 3 11 12 10 9 10 52 10.4 3 4 12 8 6 9 12 47 9.4 6 5 11 10 6 14 11 52 10.4 8 6 7 7 10 4 11 39 7.8 7 7 10 7 4 10 10 41 8.2 6 8 8 11 11 7 7 44 8.8 4 9 8 11 8 14 12 53 10.6 6 10 12 9 12 17 11 61 12.2 8 11 7 7 9 17 13 53 10.6 10 12 9 9 4 4 11 37 7.4 7 13 10 12 12 12 12 58 11.6 2 14 8 11 9 6 8 42 8.4 5 15 10 13 9 4 9 45 9 9 16 9 11 8 5 11 44 8.8 6 Total 150.6 102

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