Colonel Electric is a large company that produces lightbulbs and other electrical products. One particular lightbulb is supposed to have an average life of about 1,000 hours before it burns out. Periodically the company will test 5 of these and measure the average time before these burn out. The following table gives the results of 10 such samples:
Sample Mean Range
1 979 50
2 1087 94
3 1080 57
4 934 65
5 1072 135
6 1007 134
7 952 101
8 986 98
9 1063 145
10 958 84
A) What is the overall average of these means?
B) What are the upper and lower control limits for a 99.7% control chart for the mean?
C) Does this process appear to be in control? Explain.
D) Develop upper and lower control limits for the range. Do these samples indicate that the process is in control?
Please refer to the attachment for full solutions.
a) The overall average of these means is 1011.8.
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