The I-MR-R/S uses both between-subgroup and within-subgroup variations to generate three control charts, the individuals, moving range and R or S charts. It is useful when the overall process variation is due to both between subgroup variation and random error.
The individuals chart plots the subgroup means as individual values to remove variation within subgroup and is used to track process level. The moving range chart plots the subgroup means using a moving range to remove variation within subgroup variation and is used to track process variation between subgroups. The R or S chart plots on the other hand uses variation within subgroup to track process variation within subgroups. The R chart is used when the subgroup size is small or Rbar is used to estimate process variation. The S chart is used when subgroup size is larger or when Sbar is used to estimate process variation.
At the Excel Menu (For Excel 2007, go to Add-ins first)
Choose ProcessMA > Control Charts > Variables Charts for Subgroups > I-MR-R/S
In Variable, select the column containing the data (Numeric)
In Subgroup, select the column containing subgroup indicators (Optional, >=2 distinct values)
In Constant Subgroup Size, enter the subgroup size if it is constant (Optional, Integer, >=2)
In Mean, enter the population proportion, otherwise it will be estimated from the sample (Optional, Numeric)
In Std Dev Between Subgroups, enter the standard deviation between subgroups, otherwise it will be estimated from the data (Optional, Numeric, >0)
In Std Dev Within Subgroups, enter the standard deviation within subgroups, otherwise it will be estimated from the data (Optional, Numeric, >0)
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 I-Lower Limit Bound, enter the bound on the lower control limit for the individuals chart (Optional, Numeric)
In I-Upper Limit Bound, enter the bound on the upper control limit for the individuals chart (Optional, Numeric)
In MR-Lower Limit Bound, enter the bound on the lower control limit for the MR chart (Optional, Numeric)
In MR-Upper Limit Bound, enter the bound on the upper control limit for the MR chart (Optional, Numeric)
In R/S-Lower Limit Bound, enter the bound on the lower control limit for the R/S chart (Optional, Numeric)
In R/S-Upper Limit Bound, enter the bound on the upper control limit for the R/S chart (Optional, Numeric)
In Phase, select the column containing the phase indicators (Optional, >=2 distinct values)
In Method (Subgroup>1), choose the method of estimating sigma when subgroup size is greater than 1
In Method (Subgroup=1), 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)
Check the various checkboxes to perform respective tests
Click OK
You are the operations manager in a production plant. You need to ensure that the dimensions of the parts manufactured are in control and within specifications. You took measurements of 10 parts from each of the 8 production lines. You want to generate a I-MR-R/S Chart to monitor the process.
Open data worksheet by choosing ProcessMA > Tools > Data
Choose ProcessMA > Control Charts > Variables Charts for Subgroups > I-MR-R/S
In Variable, select W - Parts
In Subgroup, select X - Subgroup
The process is in control within and between subgroups (production lines).
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