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184 SPC Variable Control Charts Control Limits for the MA Chart UCL = 0 + 3 * / sqrt(N) Center line LCL = 0 = 0 - 3 * / sqrt(N) 0 is the process mean is the process standard deviation, also known as sigma N is the length of the moving average used to calculate the current chart value Control Limits for the MR part of the MAMR (Moving Average/Moving Range Chart Control Limits for the R-Chart _ UCL = R + D4 * Center line = _ R LCL = 0 _ R _ R in this case is the average of the moving ranges. Where the constant D4 is tabulated in every SPC textbook for various sample sizes. Control Limits for the MS part of the MAMS (Moving Average/Moving Sigma Chart UCL Center line = _ B4 * = _ S _ _ S _
