# Statistical Quality Control-Control Charts (ISS (Statistical Services) Statistics Paper IV): Questions 6 - 8 of 31

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## Question number: 6

» Statistical Quality Control » Control Charts » Attributes

Essay Question▾

### Describe in Detail

The following are the figures of defectives in 22 lots each containing 2,000 bulbs. Obtain the 3-σ control limits for the p chart.

 425 430 216 341 225 322 280 306 337 305 356 402 216 264 126 409 193 326 280 389 451 420

### Explanation

we have n = 2000

 S. No. d 1 425 0.2125 2 430 0.215 3 216 0.108 4 341 0.1705 5 225 0.1125 6 322 0.161 7 280 0.14 8 306 0.153 9 337 0.1685 10 305 0.1525

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## Question number: 7

» Statistical Quality Control » Control Charts » Variable

Essay Question▾

### Describe in Detail

A electric Company uses a process to paint cars with a coat of enamel. During each shift, a sample of five cars is selected and the thickness of the paint in mm is determined. On the basis of and R charts, Check whether the production is under control?

 Sample No. Observations 1 2.6 2.3 2.6 2.7 2.7 2 2.6 2.6 2.4 2.8 2.3 3 2.4 2.3 2.4 2.5 2.3 4 2.7 2.4 2.3 2.6 2.8 5 2.6 2.6 2.5 2.8 2.1 6 2.2 2.2 2.7 2.3 2.6 7 2.0 2.6 2.4 2.2 2.3 8 2.5 2.6 2.6 2.7 2.8 9 2.4 2.4 2.2 2.8 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 2.0 2.8 2.3 1.8 2.9

### Explanation

 Sample No. Observations Total Sample Mean () Sample Range (R) 1 2.6 2.3 2.6 2.7 2.7 12.70 2.54 0.40 2 2.6 2.6 2.4 2.8 2.3 12.70 2.54 0.50 3 2.4 2.3 2.4 2.5 2.3 11.90 2.38 0.20 4 2.7 2.4 2.3 2.6 2.8 12.80 2.56 0.50 5 2.6 2.6 2.5 2.8 2.1 12.60 2.52 0.70 6 2.2 2.2 2.7 2.3 2.6 12.00 2.40 0.50 7 2.0 2.6 2.4 2.2 2.3 11.50 2.30 0.60 8 2.5 2.6 2.6 2.7 2.8 13.20 2.64 0.30 9 2.4 2.4 2.2 2.8 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 2.0 2.8 2.3 1.8 2.9 11.80 2.36 1.10 Total 50.28 15.40

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## Question number: 8

» Statistical Quality Control » Control Charts » Variable

Essay Question▾

### Describe in Detail

Six samples, which contain 20 observations per sample, have been collected and the sample means and sample ranges are computed as shown below. Test whether the sample means are within control limits for ?

 Sample Mean Range 1 3.06 0.42 2 3.15 0.5 3 3.11 0.41 4 3.13 0.46 5 3.06 0.46 6 3.09 0.45

### Explanation

The sample size here is 20.

We are given that

 Sample Mean ( Range (R) 1 3.06 0.42 2 3.15 0.5 3 3.11 0.41 4 3.13 0.46 5 3.06 0.46 6 3.09 0.45

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