The Z-MR Chart is made up of a control chart of standardised individual observations and the Moving Range Chart. It allows you to track both process level and process variation at the same time. The Z-MR is useful for processes with insufficient data on each run to give a good estimate of process parameters. Individual observations are therefore standardised so that data collected from different runs can be evaluated on the same control chart.
At the Excel Menu (For Excel 2007, go to Add-ins first)
Choose ProcessMA > Control Charts > Variables Charts for Individuals > Z-MR
In Variable, select the column containing the data (Numeric)
In Part Indicators , select the column containing part indicators (>=2 distinct values)
In Control Limit Multiples, enter the position to draw the upper and lower control limits. Multiple entries must be separated by commas (Optional, Numeric, >0, Up to 3 multiples)
In Lower Limit Bound, enter the bound on the lower control limit (Optional, Numeric)
In Upper Limit Bound, enter the bound on the upper control limit (Optional, Numeric)
In Group Method, choose the grouping method of estimating sigma
In Method, choose the method of estimating sigma when subgroup size is equals to 1
In Moving Range Length, enter the number of observations used to calculate the moving range (Integer, >=2)
Click OK
You work in a mill and you are in-charge of quality control. The mill cuts wood into specific dimensions and dimension settings are changed according to customer’s order. You want to use the Z-MR Chart to assess if the wood is cut into the correct dimensions. You know that the variation in your process is dependent on the type of wood used.
Open data worksheet by choosing ProcessMA > Tools > Data
Choose ProcessMA > Control Charts > Variables Charts for Individuals > Z-MR
In Variable, select Z - Dimension
In Part Indicators , select AA - Wood
Click OK
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