Quality Advisor

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

Target Z, Zupper, and Zlower formulas

Target Z

Target Z formula

Zupper

Zupper formula

Zlower

Zlower formula

Where:

= 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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