Overview 

Definitions 

Factors for Control charts. 

Moving average calculations. 

Exponentially weighted moving average chart calculations. 
Moving averages are generally used to smooth out the noise in a time series and forecast future values of the series.
A MA (Moving Average) chart can be drawn based on either:
Subgroup means or
Individual observations (Subgroup size =1).
A moving average is calculated by averaging consecutive groups of observations in a series.
Example
A series begins with the numbers 8,9,10,11, and 12 and the moving average length is 3.
The values of the moving average are as follows:
Value 
Is 
First 
Missing 
Second 
Missing 
Third 
8,9, and 10 
Fourth 
9,10, and 11 
Fifth 
10, 11, and 12 and so on. 
Terms used in moving average calculations are:
Subgroup Size 
A set of one or more observations that are used to calculate a value on an SPC chart. Any subgroup size between 1 and 10 can be selected on the Chart tab in the SPC Control Properties dialog box. 
Length of MA 
Length of the moving averages. The value that is specified will be the number of subgroup means that will be included in each average. Any Length between 1 and 24 can be selected on the Chart tab in the SPC Control Properties dialog box. 
Weighting Factor 
Weight to be used in the exponentially weighted moving average. The value specified must be a number between 0 and 1. 
Charts
Exponentially weighted moving average chart calculations. 

Moving average calculations. 

Moving range calculations. 
SPC chart calculations. 