T20-01 - 1

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T20-01 Mean Chart (Known Variation) CL
Calculations
Purpose Allows the analyst calculate the "Mean
Chart" for known variation 3-sigma control
limits. Inputs Sample Size Centerline
(Grand Average) Process Standard
Deviation Outputs Mean
Control Chart LCL UCL
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Mean Chart ( Chart) - Known Variation
The Mean Chart Centerline, UCL and LCL (3 sigma
limits) are calculated by the following when the
variation of the process is known.
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Example
The mean of 20 samples each containing 5
observations are shown here. They have been
taken from a process with known variance of .04.
The grand average can now be calculated. This
can be done by using the Descriptive Statistics
Template or more quickly by using the EXCEL built
in AVERAGE function on this set of
numbers. Calculate the Control Limits for the
Mean Control Chart.
Grand Average
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Input the Sample Size, Centerline (Grand
Average), and Process Standard Deviation in the
light green cells.