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The SHEWHART Procedure


The IRCHART statement creates control charts for individual measurements and moving ranges. These charts are appropriate when only one measurement is available for each subgroup sample and when the measurements are independently and normally distributed.

You can use options in the IRCHART statement to

  • compute control limits from the data based on a multiple of the standard error of the individual measurements and moving ranges or as probability limits

  • tabulate individual measurements, moving ranges, and control limits

  • save control limits in an output data set

  • save individual measurements and moving ranges in an output data set

  • read preestablished control limits from a data set

  • apply tests for special causes (also known as runs tests and Western Electric rules)

  • specify a known (standard) process mean and standard deviation for computing control limits

  • specify the number of consecutive measurements to use when computing the moving ranges

  • display distinct sets of control limits for data from successive time phases

  • add block legends and symbol markers to reveal stratification in process data

  • superimpose stars at points to represent related multivariate factors

  • clip extreme points to make the chart more readable

  • display vertical and horizontal reference lines

  • control axis values and labels

  • control layout and appearance of the chart

You have three alternatives for producing charts of individual measurements and moving ranges with the IRCHART statement:

  • Traditional graphics are produced by default.

  • ODS Graphics output is produced when you specify the ODS GRAPHICS statement prior to the PROC SHEWHART statement.

  • Legacy line printer charts are produced when you specify the LINEPRINTER option in the PROC SHEWHART statement.

See Chapter 3, SAS/QC Graphics, for more information about producing these different kinds of graphs.

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