Interpretation & Calculations
A Moving Average Sigma Chart from SPC IV Excel software.
Moving Average / 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 Moving Average chart monitors the process location over time, based on the average of the current subgroup and one or more prior subgroups. The Moving Sigma chart monitors the variation between the subgroups over time and it can be analyzed using Moving Average software.
The plotted points for a Moving Average / Sigma Chart, called a cell, include the current subgroup and one or more prior subgroups. Each subgroup within a "cell" may contain one or more observations, but must all be of the same size.
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).