Statistical Quality Control (ISS Statistics Paper IV): Questions 9 - 11 of 34

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Question number: 9

» 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 X¯chart ?

Test mean samples and check if they are in control limits

Test mean samples and check if they are in control limits

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

Calculating mean and range to test mean samples and check if they are in control limits

Test mean samples and check if they are in control limits Mean and range

Sample

Mean ( X¯i)

Range (R)

1… (160 more words) …

Question number: 10

» Statistical Quality Control » Control Charts » Variable

Essay Question▾

Describe in Detail

Construct a control chart for mean for the following data based on fuses, samples of 5 being taken every hour. Check whether the production is under control?

Given are observations find whether the production is under control

Given are observations Is whether the production is under control?

Sample No.

Observations

1

42

65

75

78

87

87

2

42

45

68

72

90

90

3

19

24

80

81

81

81

4

36

54

69

77

84

84

5

42

51

57

59

78

78

6

51

74

75

78

132

132

7

60

60

72

95

138

138

8

18

20

27

42

60

60

9

15

30

39

62

84

84

10

69

109

113

118

153

153

11

64

90

93

109

112

112

12

61

78

94

109

136

136

Total

859.2

716

Explanation

Given are observations Calculating if production is under control

Given are observations Production is under control

Sample No.

Observations

Total

Sample Mean ( X¯)

Sample Range

1

42

65

75

78

87

87

347

69.4

45

2

42

45

68

72

90

90

317

63.4

48

3

19… (254 more words) …

Question number: 11

» Statistical Quality Control » Acceptance Sampling by Attributes

Essay Question▾

Describe in Detail

a) What is the small percentage of defects that consumers are willing to accept?

b) What is upper limit of the percentage of defective items consumers are willing to tolerate?

c) What is probability that a lot will be accepted that contains a greater number of defects than the LTPD limit known as?

Explanation

a) The small percentage of defects that consumers are willing to accept is known as Acceptance Quality level (AQL).

If p1is a lot with relatively small fraction defective, that we do not wish to reject then

P (rejecting a lot of quality p1) = 0.05 Or… (142 more words) …

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