PCHART Statement: SHEWHART Procedure

Overview: PCHART Statement

The PCHART statement creates p charts for the proportions of nonconforming (defective) items in subgroup samples.

You can use options in the PCHART statement to

  • compute control limits from the data based on a multiple of the standard error of the proportions or as probability limits

  • tabulate subgroup sample sizes, proportions of nonconforming items, control limits, and other information

  • save control limits in an output data set

  • save subgroup sample sizes and proportions of nonconforming items 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) proportion of nonconforming items for computing control limits

  • specify the data as counts, proportions, or percentages of nonconforming items

  • 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 p charts with the PCHART statement:

  • ODS Graphics output is produced if ODS Graphics is enabled, for example by specifying the ODS GRAPHICS ON statement prior to the PROC statement.

  • Otherwise, traditional graphics are produced by default if SAS/GRAPH® is licensed.

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

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