CPCHART Subcommand (SPCHART command)

CPCHART produces a process capability chart. The default process capability chart consists of a histogram of the process values, a superimposed normal curve based on the capability sigma and the process mean, and vertical reference lines at the fixed upper and lower control limits and target value (if specified). It also displays the process capability indices, the process performance indices, and process data such as the process mean and process standard deviation.

  • When CPCHART is specified the LSL and USL subcommands are required. The TARGET subcommand is optional with CPCHART.
  • You can control which normal curves are superimposed on the histogram with the NORMAL subcommand.
  • You can display vertical reference lines at the plus or minus three sigma level, or a user-specified sigma level, with the REFERENCE subcommand.
  • All of the statistics displayed on the process capability chart are available in table form from the STATISTICS subcommand.
  • Process capability charts have a default title of Process Capability. You can specify your own title using the TITLE and SUBTITLE subcommands.
Figure 1. Process capability chart
Process capability chart