Interpretation & Calculations
An X-bar & Sigma Chart with process capability estimates from SPC IV Excel software.
X-bar & Sigma Charts are a set of control charts for variables data (data that is both quantitative and continuous in measurement, such as a measured dimension or time). The X-bar chart monitors the process location over time, based on the average of a series of observations, called a subgroup. The Sigma chart monitors the variation between observations in the subgroup over time.
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).