Moving Average Chartoverview how to example data see also
Moving Average ChartStat > Control Charts > Time-weighted Charts > Moving Average
A moving average chart is a chart of moving averages - averages calculated from artificial subgroups that are created from consecutive observations. The observations can be either individual measurements or subgroup means. This chart is generally not preferred over an EWMA chart because it does not weight the observations as the EWMA does.
When data are in subgroups, the mean of all the observations in each subgroup is calculated. Moving averages are then formed from these means. By default, the process standard deviation, s, is estimated using a pooled standard deviation. You can also base the estimate on the average of subgroup ranges or subgroup standard deviations, or enter a historical value for s.
When you have individual observations, moving averages are formed from the individual observations. By default, s is estimated s, with MR / d2, the average of the moving range divided by an unbiasing constant. Moving ranges are artificial subgroups created from consecutive measurements. The moving range is of length 2, since consecutive values have the greatest chance of being alike. You can also estimate s using the median of the moving range, change the length of the moving range, or enter a historical value for s.
For more information, see Control Charts Overview and Time-Weighted Control Charts Overview.
All observations for a chart are in one column: Choose if data are in one or more columns, then enter the columns.
Subgroup sizes: Enter a number or a column of subscripts. If the subgroups are not equal, each control limit is not a single straight line but varies with the subgroup size. If the subgroup sizes do not vary much, you may want to force the control limits to be constant by specifying a fixed subgroup size using MA Option > Limits.
Observations for a subgroup are in one row of columns: Choose if subgroups are arranged in rows across several columns, then enter the columns.
Length of MA: Enter the length of the moving averages. The value you enter is the number of subgroup means to be included in each average. If you have individual observations (that is, you specified a subgroup size of 1), Minitab uses them in place of the subgroup means in all calculations.