Question: A quality analyst wants to construct a sample mean chart for controlling a packaging process. Each day last week, he randomly selected six packages and
A quality analyst wants to construct a sample mean chart for controlling a packaging process. Each day last week, he randomly selected six packages and weighed each. The data from that activity appears below.
|
| Weight (in grams) |
|
| |||
| Day | Package 1 | Package 2 | Package 3 | Package 4 | Package 5 | Package 6 |
| Monday | 23 | 22 | 23 | 24 | 23 | 21 |
| Tuesday | 23 | 21 | 19 | 21 | 24 | 20 |
| Wednesday | 20 | 19 | 20 | 21 | 19 | 20 |
| Thursday | 18 | 19 | 20 | 19 | 21 | 22 |
| Friday | 18 | 20 | 22 | 20 | 19 | 21 |
To assist students, I am attaching the Factors for Determining Control Limits from your text
Sample size A2 D3 D4
2 1.880 0 3.268
3 1.023 0 2.574
4 0.729 0 2.282
5 0.577 0 2.115
6 0.483 0 2.004
7 0.419 0.076 1.924
8 0.373 0.136 1.864
9 0.337 0.184 1.816
10 0.308 0.223 1.777
12 0.266 0.284 1.716
Assuming three (3) sigma limits (corresponding to 99.73 percent), construct:
- the upper and lower control limits for a Mean chart; (3 marks)
- the upper and lower control limits for a Range chart; (3 marks)
Examining the data and your constructed charts from above, is the process in control, heading out of control or already out of control? Briefly justify your answer in no more than 1-2 sentences (60 words maximum).
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