Statistical Quality Control (ISS Statistics Paper IV): Questions 18 - 20 of 34

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Question number: 18

» 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 X¯ chart, Check whether the production is under control?

Find whether production is under control for mica discs

Find whether production is under control for mica discs

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

Find whether production is under control for mica discs Total, Mean and Range

Find whether production is under control for mica discs

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… (259 more words) …

Question number: 19

» Statistical Quality Control » Control Charts » Variable

Essay Question▾

Describe in Detail

a) If the average range for the 4 samples is 0.2 millimeters and the average mean of the observations is 12.5 millimeters, obtain the three-sigma control limits for the sample mean.

b) 5 observations have been taken from the10 samples in order to test the volume in the bags. The average sample range is 0.5 ounces. Obtain the 3-σ limits for the sample range.

Explanation

a) It is given that n = 5 X¯=12.5 and R¯=0.2

For n = 5, The value of A2=0.58

Control limits for X¯chart:

CLX¯=X̿=12.5

UC… (120 more words) …

Question number: 20

» Statistical Quality Control » Control Charts » Variable

Essay Question▾

Describe in Detail

A new oven has been installed in a bakery and to test the efficiency of this, the oven temperature readings have been taken at four different places inside the oven every 30 min. The following table gives readings. Determine the control limits for the mean temperature.

Determine the control limits for the mean temperature

Determine the control limits for the mean temperature

Time

Readings

8: 00

400

500

550

390

8: 30

440

420

380

380

9: 00

410

450

470

430

9: 30

390

390

410

410

10: 00

370

420

460

410

10: 30

390

400

390

400

Explanation

Determine the control limits for the mean temperature Total, Mean and Range

Determine the control limits for the mean temperature

Readings

Total

Sample mean

Sample Range

400

500

550

390

1840

460

160

440

420

380

380

1620

405

60

410

450

470

430

1760

440

60

390

390

410… (132 more words) …

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