One-pound coffee cans are filled by a machine, sealed, and then weighed automati
ID: 355401 • Letter: O
Question
One-pound coffee cans are filled by a machine, sealed, and then weighed automatically. After adjusting for the weight of the can, any package that weighs less than 16 oz is cut out of the conveyor. The weights (oz) of 24 successive cans are measured and the average weight and moving range for these cans are 16.11 oz and 0.04 oz respectively.
a. Establish the control limits for a moving range control chart and a control chart for individuals, assuming that all points will plot inside the trial control limits.
b. Estimate the mean and standard deviation of the amount of coffee packed in each can.
c. If the process remains in control at this level, what percentage of cans will be underfilled?
Explanation / Answer
a)
Moving Range UCL = 3.27 * Rbar = 3.27 * 0.04 = 0.1308
Moving Range UCL = none
Individual UCL = Average + 2.66 * Rbar = 16.11 + 2.66 * 0.04 = 16.23
Individual LCL = Average - 2.66 * Rbar = 16.11 - 2.66 * 0.04 = 16.00
b) since assumption is all trial plots will be inside graph limits
Standard Deviation = Rbar / 1.128 = 0.04 / 1.128 = 0.035
Mean = 16.11
c)
Since lower limil of process is 16.0, there will be no cans underfilled.
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