Aces High Bulletin Board
General Forums => The O' Club => Topic started by: Raptor on February 12, 2010, 12:10:06 AM
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I have not done statistics in 4 years and I am having difficulty understanding where a number comes from:
A soda company bottles soft drinks into 16oz bottles. The overall process average is 16.1oz, which was found by taking a large number of samples, with each sample consisting of 5 bottles. The average range of the process sampleis .25oz. Using 3σ control limits, calculate the c-bar chart upper limit and lower limit control limits for the process.
From this I got:
mean = 16.1
range = .25
I know for the upper control I use:
UCL=Mean + (A)(Range)
UCL=16.1+(.577)(.25)
resulting in 16.244oz. which means the sample is in control.
What I do not understand is what A stands for or how I got it. It has something to do with sigma which I am just missing entirely.
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ok nevermind I got it...
A2 = constant to provide three-sigma limits for the sample mean
So I had to pull it from a chart.
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Yup, exactly what I was going to say. :noid
:bolt:
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Man, you beat me by half a second...