Statistical Quality Control-Control Charts (ISS Statistics Paper IV): Questions 23 - 25 of 31

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Question number: 23

» Statistical Quality Control » Control Charts » Variable

Essay Question▾

Describe in Detail

a) What is major difference between X bar Chart and R chart?

b) What is OC plot?

c) What is Average outgoing Quality (AOQ)?

d) What is Average Total Inspection (ATI)?

Explanation

a) X¯chart is used to control the process mean, R chart is used to control process variation. X¯chart reveals undesirable variations between samples as far as their averages are concerned while the R chart reveals any undesirable variations… (263 more words) …

Question number: 24

» Statistical Quality Control » Control Charts » Attributes

Essay Question▾

Describe in Detail

a) In welding of seams, defects included pinholes, cracks, cold laps, etc. A record was made of the number of defects found in one seam each hour and given below. Obtain the 3-σ limits for number of defects.

Finding limits for number of defects

Finding limits for number of defects

1/12/1983

8 A. M.

2

12 A. M.

6

9 A. M.

4

1 P. M.

4

10 A. M.

7

2 P. M.

9

11 A. M.

3

3 P. M.

9

12 A. M.

1

3/12/1983

8 A. M.

6

1 P. M.

4

9 A. M.

4

2 P. M.

8

10 A. M.

3

3 P. M.

9

11 A. M.

9

2/12/1983

8 A. M.

5

12 A. M.

7

9 A. M.

3

1 P. M.

4

10 A. M.

7

2 P. M.

7

11 A. M.

11

3 P. M.

12

b) The number of daily customer complaints are monitored at a telephone exchange. Complaints have been recorded over the past twenty days. Develop three-sigma control limits for the following data.

Number of days and complains per day

Finding control limits for the given data

Days

No. of complaints

Days

No. of complaints

1

2

11

1

2

3

12

3

3

1

13

2

4

3

14

1

5

3

15

1

6

2

16

1

7

3

17

3

8

1

18

2

9

1

19

2

10

3

20

4

Explanation

a) Average number of defects per sample is

c¯=14424=6

CLc=c¯=6

UCLc=c¯+3c =6+ 36 =13.35

LCLc=c¯3c =6- 36… (93 more words) …

Question number: 25

» 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. Based on R chart, Check whether the production is under control?

Find whether production is under control for R chart

Find whether production is under control for mica discs

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

Find whether production is under control for R chart - mica Total, Mean and Range

Find whether production is under control for mica discs

Sample No.

Observations

Sample Range

1

8

9

15

4

11

11

2

7

10

7

6

8

4

3

11

12

10

9

10

3… (189 more words) …

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