Range Chart Calculations
Plotted statistic
Rangej = MAX (x1, x2,…, xn) - MIN (x1, x2,…, xn)
where x1, x2, … are the n observations in the subgroup j
Center Line
UCL , LCL (Upper and Lower Control Limit)
where R-bar is the Average Range , d3 is a function of n, and σx is Process Sigma, which is calculated using the Subgroup Range .
Notes: Some authors prefer to write this calculation for statistical process charts as:
