ISS (Statistical Services) Statistics Paper IV: Questions 28 - 30 of 92

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Question number: 28

» Statistical Quality Control » Control Charts » Attributes

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Essay Question▾

Describe in Detail

The following are the figures of defectives in 22 lots each containing 2,000 bulbs. Ind control limit for p-Chart.

Lot of 2000 bulbs with those defective

Finding the correct answer from the choices given below

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

Lot of 2000 bulbs with those defective Solving in table we have

Finding the correct answer from the choices given below

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

11

356

0.178

12

402

0.201

13

216

0.108

14

264

0.132

15

126

0.063

16

409

0.2045

… (243 more words) …

Question number: 29

» Statistical Quality Control » Control Charts » Attributes

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Essay Question▾

Describe in Detail

Each day a sample of 1500 items from a production process was examined. The number of defectives found in each sample was as follows. With a suitable control chart, check out for control 4,6, 6,2, 15,4, 4

Explanation

We have n = 30

Find whether production is under control for 1500 items Total, Mean and Range

Find whether production is under control for 1500 items

S. No.

d

1

4

0.00267

2

6

0.00400

3

6

0.00400

4

2

0.00133

5

15

0.01000

6

4

0.00267

7

4

0.00267

Total

41

0.02733

Control limits for charts

… (252 more words) …

Question number: 30

» Statistical Quality Control » Control Charts » Variable

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Essay Question▾

Describe in Detail

a) The number of customer complaints are recorded at a television manufacturing company. Complaints have been recorded over the past 20 weeks. Construct 3-σ control limits for the c-chart.

Construct 3 sigma control limit for c-chart

What is the 3 sigma control limit for c-chart

Week

No. of complaints

Week

No. of complaints

1

0

11

4

2

3

12

3

3

4

13

1

4

1

14

1

5

0

15

1

6

0

16

0

7

3

17

2

8

1

18

1

9

1

19

2

10

0

20

2

b) A machine is manufacturing mica discs. samples of size 5 are drawn every hour and their thickness in units are recorded as follows. From this data construct 3-σ control limits for chart.

Construct 3 sigma control limit for x bar-chart

What is the 3 sigma control limit for x bar-chart

Sample No.

Observstions

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

a) Average number of defects per sample is

=1.5+ =1.5 + 3 (1.22) =5.174

= →0

Since number of defects cannot be negative, can be considered as zero. (rounded up to z

… (217 more words) …

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