The Process Performance Indices (SPCHART command)

PP. Performance of the process.

PPU. The distance between the process mean and the upper specification limit scaled by process standard deviation.

PPL. The distance between the process mean and the lower specification limit scaled by process standard deviation.

PPK. Performance of the process related to both dispersion and centeredness. It is the minimum of PpU and PpL. If only one specification limit is provided, we compute and report a unilateral PpK instead of taking the minimum.

PR. The reciprocal of PP.

PPM. An index relating process variance and the difference between the process mean and the target value. A target value must be specified on the TARGET subcommand by the user.

PZU. The number of standard deviations between the process mean and the upper specification limit.

PZL. The number of standard deviations between the process mean and the lower specification limit.

PZMIN. The minimum number of standard deviations between the process mean and the specification limits.

PZMAX. The maximum number of standard deviations between the process mean and the specification limits.

PZOUT. The estimated percentage outside the specification limits. The standard normal approximation is based on PZ _U and PZ _L.

PZLOUT. The estimated percentage outside the lower specification limit. The standard normal approximation is based on PZ _L.

PZUOUT. The estimated percentage outside the upper specification limit. The standard normal approximation is based on PZ _U.

• For each of the keywords (other than PPK), both the LSL subcommand and the USL subcommand must be specified. Otherwise, we ignore the keyword(s) and issue a syntax warning. For PPK, at least one of the LSL and USL subcommands must be specified.
• If the TARGET subcommand is not specified, the keyword PPM is ignored, and a syntax warning is issued.