The Moving Average Chart is a control chart of moving averages (of individuals or subgroup means). It is used to track the process level and detect signs of special causes.
1. Choose ProcessMA > Control Charts > Time-Weighted Charts > Moving Average.
2. In Variable, select the column containing the data.
· For constant subgroup size:
- Check Constant size.
- In Subgroup, enter the subgroup size.
· For non-constant subgroup size:
- Uncheck Constant size.
- In Subgroup, select the column containing the subgroup codes.
3. In Moving average length, enter the length of the moving averages.
4. Click OK.
Optional
5. In Mean, enter the population mean, otherwise it will be estimated by the sample mean.
6. In Standard deviation, enter the population standard deviation, otherwise it will be estimated from the data.
7. In Control limit multiples, enter the position to draw the upper and lower control limits. Multiple entries must be separated by commas (,).
8. In Lower limit bound, enter the bound on the lower control limit.
9. In Upper limit bound, enter the bound on the upper control limit.
10. In Phase, select the column containing the phase codes. (Phase can useful to compare groups of data like before and after improvement)
11. In Method (Subgroup size=1), select the method of estimating sigma when subgroup size is 1.
· Average moving range Estimate based on the average of the moving range.
· Median moving range Estimate based on the median of the moving range
12. In Method (Subgroup size>1), select the method of estimating sigma when subgroup size is greater than 1.
· Rbar - Estimate based on the average of the subgroup ranges.
· Sbar -Estimate based on the average of the subgroup standard deviations.
· Pooled standard deviation - Estimate based on pooled standard deviation.
13. In Moving range length, enter the number of observations used to calculate the moving range.
Note To select a column of data into a textbox, double-click on any of the column names shown in the list on the left of the dialog box while in the textbox.
Variable: Numeric.
Subgroup (For non-constant subgroup size): Text or Numeric; Must contain equal number of data points as the Variable.
Subgroup (For constant subgroup size): Integer; Must be at least 2.
Mean: Numeric.
Standard deviation: Numeric.
Control limit multiples: Numeric.
Lower limit bound: Numeric.
Upper limit bound: Numeric.
Moving average length: Integer.
Phase: Text or Numeric; Must contain equal number of data points as the Variable.
You collected cycle time data for application approval. You want to monitor the process using a Moving Average Chart.
1. Open worksheet ProcessMA > Tools > Data Files > Control.xls.
2. Choose ProcessMA > Control Charts > Time-Weighted Charts > Moving Average.
3. In Variable, select K Approval time.
4. Check Constant size.
5. In Subgroup, enter 1
6. Click OK.
