Methods and formulas for overall capability measures in Normal Capability Analysis for Multiple Variables

Pp

Notation

TermDescription
USLUpper specification limit
LSLLower specification limit
TolerMultiplier of the sigma tolerance (Minitab uses 6 as the default value)
Overall standard deviation

PPL

Notation

TermDescription
Process mean (estimated from the sample data or a historical value)
LSLLower specification limit
TolerMultiplier of the sigma tolerance (Minitab uses 6 as the default value)
Overall standard deviation

PPU

Notation

TermDescription
USLUpper specification limit
Process mean (estimated from the sample data or a historical value)
TolerMultiplier of the sigma tolerance (Minitab uses 6 as the default value)
Overall standard deviation

Ppk

Cpm

Cpm is available only when a target is specified. Minitab calculates Cpm based on known values of LSL, USL, and T.

Known value Cpm
LSL and USL only *
LSL, USL, and T = m
LSL, USL, and T ≠ m
USL and T only
LSL and T only
Either LSL or USL only *

Notation

TermDescription
*Missing value
USLUpper specification limit
LSLLower specification limit
mMidpoint between USL and LSL
TTarget value
Xijjth observation in the ith subgroup
niNumber of observations in the ith subgroup
TolerMultiplier of the sigma tolerance (Minitab uses 6 as the default value)
By using this site you agree to the use of cookies for analytics and personalized content.  Read our policy