Control charts from summary statistics

This macro uses summarized data to produce an Xbar chart and either an R chart or an S chart.

Download the Macro

Be sure that Minitab knows where to find your downloaded macro. Choose Tools > Options > General. Under Macro location browse to the location where you save macro files.

Important

If you use an older web browser, when you click the Download button, the file may open in Quicktime, which shares the .mac file extension with Minitab macros. To save the macro, right-click the Download button and choose Save target as.

Required Inputs

  • One value or a column of mean values
  • One value or a column of subgroup sizes
  • One value or a column of standard deviations or ranges

Optional Inputs

TEST K
Use to specify non-default tests (1-8) for special causes.
  • 1 - One point more than 3 sigmas from center line
  • 2 - Nine points in a row on same side of center line
  • 3 - Six points in a row, all increasing or all decreasing
  • 4 - Fourteen points in a row, alternating up and down
  • 5 - Two out of three points more than 2 sigmas from center line (same side)
  • 6 - Four out of five points more than 1 sigma from center line (same side)
  • 7 - Fifteen points in a row within 1 sigma of center line (either side)
  • 8 - Eight points in a row more than 1 sigma from center line (either side)
HPROCESS C
Use to specify a historical grouping column to define historical stages in the process data. The control limits and center line are then estimated independently within each stage. Stages are much like groups in other Minitab graph commands. Thus, the HPROCESS column is like a group variable in other graph commands, with one exception -- whenever the value in the column changes, a new stage starts. This works the same way the subgroup column works in the control chart commands.

Running the Macro

Suppose C1 contains the means, the subgroups were all of size 3, and C3 contains the ranges for each subgroup. To run the macro, choose Edit > Command Line Editor and type:

%QCSUMMARY;
MEAN C1;
RANGE C3;
SIZE 5.

Click Submit Commands.

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