Nonconforming units

Nonconforming units describe the number of nonconforming units a process produces, expressed in parts per million.

The number of nonconforming units is an alternative to traditional Cp and Pp indices. They are easily understandable by end-users.

The number of nonconforming units is either:

The actual number of nonconforming units in the sample.
The expected number of nonconforming units, assuming a normally distributed process quality characteristic with the parameters specified by the process mean and sigma. The process sigma is either the short-term or long-term sigma estimate.

Various indices measure how the process is performing against the specification limits:

Index	Description
< LSL	The number of nonconforming units that are less than the lower specification limit.
> USL	Thr number of nonconforming units that are greater than the upper specification limit.
< SL >	The total number of nonconforming units that are outside the specification limits.

Related tasks

Estimating process capability

Available in Analyse-it Editions
Quality Control & Improvement edition
Ultimate edition