Methods and formulas for expected within performance in Normal Capability Analysis for Multiple Variables

PPM < LSL for expected "within" performance

The expected number of parts per million that are less than the lower specification limit, based on the variation within the subgroups, is

Notation

TermDescription
PPMParts per million
LSLLower specification limit
Φ (X) Cumulative distribution function (CDF) of a standard normal distribution
Average of the observations
Within-subgroup standard deviation

PPM > USL for expected "within" performance

The expected number of parts per million that are greater than the upper specification limit, based on the variation within the subgroups, is

Notation

TermDescription
PPMParts per million
USLUpper specification limit
Φ (X) Cumulative distribution function (CDF) of a standard normal distribution
Average of the observations
Within-subgroup standard deviation

PPM Total for expected "within" performance

The expected number of parts per million that are outside the specification limits, based on the variation within the subgroups, is

Notation

TermDescription
PPMParts per million
LSLLower specification limit
USLUpper specification limit
Φ (X) Cumulative distribution function (CDF) of a standard normal distribution
Average of the observations
Within-subgroup standard deviation
By using this site you agree to the use of cookies for analytics and personalized content.  Read our policy