The number of conforming units incorrectly marked for rejection divided by the conforming units checked.
Also called: false rejection rate; false positive rate.
How is false-reject rate calculated?
False-reject rate is the fraction of reference-conforming units incorrectly marked for rejection. When positive means the target defect is detected, it is the false-positive fraction among reference-negative units, or one minus specificity.
The unit may be a bottle or another inspected unit, but it must stay consistent. The formula cannot be estimated from a group containing no reference-conforming units.
False-reject rate = conforming units incorrectly marked for rejection / all reference-conforming units checked
Does an incorrect reject decision prove a bottle was removed?
No. Keep the decision record separate from the physical reject outcome. An inspection signal and a reject-confirmation signal describe different parts of the process.
Check reject timing and diversion against the identified bottles. Evaluate missed defects separately: a low false-reject rate measures how conforming units were classified, not how many defective units escaped.