Flag a recorded length below 30 cm OR above 40 cm. Both endpoints stay unflagged. A review band is not a physical size limit. Classify the flag and correctness separately: a flag with agreement is a false alarm; a flag with disagreement catches an error; no flag with disagreement misses an error. Only a supplied independent check establishes agreement here. The checks are assumed reliable in this invented exercise, not a claim that real measurements are perfect.
Worked example
Under a different 70 to 80 cm band, a recorded 82 cm and a checked 82 cm give a false alarm. A recorded 76 cm and a checked 77 cm give a missed error. A record of 70 cm without a check is unflagged, but its correctness remains unknown.
Evidence file
Invented crate records (recorded length / independent check): J: 44 cm / 44 cm. K: 26 cm / 34 cm. L: 36 cm / 37 cm. M: 30 cm / 30 cm. N: 40 cm / missing. Apply the below-30 OR above-40 review rule to each recorded length.