Interpretation & Calculations
UCL , LCL (Upper and Lower Control Limit)
Notes: Some authors prefer to write this x-bar chart formula as:
where R-bar is the Average Range , or
where S-bar is the Average Sigma .
Learn more about the SPC principles and tools for process improvement in Statistical Process Control Demystified (2011, McGraw-Hill) by Paul Keller, in his online SPC Concepts short course (only $39), or his online SPC certification course ($350) or online Green Belt certification course ($499).