Question: A quality analyst wants to construct a sample mean chart for controlling a packaging process. He knows from past experience that the process standard deviation
A quality analyst wants to construct a sample mean chart for controlling a packaging process. He knows from past experience that the process standard deviation is two ounces. Each day last week, he randomly selected four packages and weighed each. The data from that activity appear below.
|
| Weight | |||
| Day | Package 1 | Package 2 | Package 3 | Package 4 |
| Monday | 23 | 22 | 23 | 24 |
| Tuesday | 23 | 21 | 19 | 21 |
| Wednesday | 20 | 19 | 20 | 21 |
| Thursday | 18 | 19 | 20 | 19 |
| Friday | 18 | 20 | 22 | 20 |
(a) Calculate all sample means and the mean of all sample means.
(b) Calculate upper and lower 2-sigma x-bar chart control limits that allow for natural variations.
(c) Based on the x-bar chart, is this process in control?
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