Statistical Details for Individual Measurement and Moving Range Charts
This section describes how control limits for Individual Measurement and Moving Range charts are calculated in Control Chart Builder.
Control limits for Individual Measurement charts are computed as follows:
LCL for Individual Measurement Chart = 
UCL for Individual Measurement Chart = 
Control limits for Individual Measurement charts with sigma estimated by the median moving range are computed as follows:
LCL for Individual Measurement Chart = 
UCL for Individual Measurement Chart = 
Control limits for Moving Range charts are computed as follows:
LCL for Moving Range Chart = 
UCL for Moving Range Chart = 
Control limits for Median Moving Range charts are computed as follows:
LCLMMR = max(0, MMR - Kd3(n)
)
UCLMMR = MMR + Kd3(n)
The standard deviation for Individual Measurement and Moving Range charts is estimated as follows:
The standard deviation for Individual Measurement and Moving Range charts when using the median is estimated as follows:
= MMR/0.954
where:
= the mean of the individual measurements
K = the sigma multiplier and is set to 3 by default
= the mean of the nonmissing moving ranges computed as (MR2+MR3+...+MRN)/(N-1) where MRi = |xi - xi-1|.
MMR = the median of the nonmissing moving ranges
σ = the process standard deviation
d2(n) = expected value of the range of n independent normally distributed variables with unit standard deviation.
d3(n) = standard deviation of the range of n independent normally distributed variables with unit standard deviation
Note: Moving Range charts in Control Chart Builder use a range span of n = 2.