Quality Advisor

A free online reference for statistical process control, process capability analysis, measurement systems analysis, control chart interpretation, and other quality metrics.

Target Z, Zupper, and Zlower formulas

Target Z

Target Z formula


Zupper formula


Zlower formula


= the mean of the X-bars
T = specification target
Sigma is an estimated sigma or sigma of the individual values, depending on how the histogram
is configured or whether you are calculating Cpk (estimated) or Ppk (actual).

Comply with critical quality standards, reduce variability, improve profitability, and reduce costs.

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