A free online reference for statistical process control, process capability analysis, measurement systems analysis, and control chart interpretation, and other quality metrics.
Theoretical percent out-of-spec formulas
To find theoretical % above spec:
Locate the value for Zupper in a standard normal table.
To find theoretical % below spec:
Locate the value for Zlower in a standard normal table.
If the Z value from the standard normal table is multiplied by 100, then this process is expected to produce X% of its output outside specification.
The standard normal table
The formulas for Target Z
The formula for actual percent out of spec
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