Glow worm is a company that produces light bulbs and other electrical products.
ID: 3055735 • Letter: G
Question
Glow worm is a company that produces light bulbs and other electrical products. One light bulb is supposed to have an average life of about 1000 hours before it burns out. Periodically, the company will test 5 of these and measure the average time before the bulbs burn out. Use the following table of 10 such samples for questions 19-22:
Sample
1
2
3
4
5
6
7
8
9
10
Mean
1000
979
1065
963
972
1052
988
999
1087
1016
Range
70
149
138
69
61
58
83
57
103
102
What are the lower and upper control limits for the R chart?
0 and 131.1
0 and 161.9
0 and 188.1
0 and 89
What is center line for the R chart?
131.1
161.9
188.1
89
What are the upper and lower control limits for the chart?
808.2 and 1,215.4
960.7 and 1,063.5
0 and 1,011.8
0 and 203.6
Is the process in control?
The range is in control so the entire process is in control
The mean is in control
Special causes of variation may be present for the process range.
Special causes of variation may be present for the process mean
If the sample size is increased 5 to 10 for computing R and X chart values?
D3 increases
D4 decreases
A2 decreases
All of the above
Sample
1
2
3
4
5
6
7
8
9
10
Mean
1000
979
1065
963
972
1052
988
999
1087
1016
Range
70
149
138
69
61
58
83
57
103
102
Explanation / Answer
1) for n=5 ; D3 =0 and D4 =2.115
hence lower limit =D3*Rbar =0
upper limit =D4*Rbar =2.115*89= 188.1
0 and 188.1 is correct
2)
center line for the R chart =Rbar =89
3)
for n=5 ; A2 =0.577
hence lower control limits =xbar -A2*Rbar =960.7
upper control limits =xbar +A2*Rbar =1063.5
960.7 and 1,063.5 is correct
4)
as value 1087 is outside control limit of mean
Special causes of variation may be present for the process mean
5)
All of the above
Sample Mean Range 1 1000 70 2 979 149 3 1065 138 4 963 69 5 972 61 6 1052 58 7 988 83 8 999 57 9 1087 103 10 1016 102 total 10121 890 average 1012.1 89Related Questions
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