In production lines, rejecting a product that is technically good represents one of the most dangerous and underestimated wastes: the false positive. This type of error does not directly compromise the quality perceived by the customer, but seriously affects the efficiency, productivity, cost, and confidence in the tests.
The incorrect detection of a fault — when there is no fault — generates unnecessary rework, blocked batches, waste of time, labor, and even improper disposal.
🔍 What is a false positive?
A false positive occurs when the test system indicates a non-existent fault. In other words, the product is good, but it was rejected due to a measurement error, test instability, poorly defined tolerance or failure in the test interface.
Common examples:
- Incorrect reading due to poor connection in the test jig
- Temporary communication error with measurement instrument
- Incorrect calibration of the sensors
- Test tolerance too tight without statistical basis
- Environment with electrical noise or vibration affecting measurements
🧾 Impacts of the false positive
- Unnecessary rework (rework)
- Increase in cycle time and lead time
- Reduction in FPY (First Pass Yield)
- Distrust of the production team in the test systems
- Additional cost with diagnosis, validation, and maintenance
- Focus deviation: technicians trying to fix something that is already correct
🎯 How to avoid rejecting good products?
AJOLLY Testing supports its clients with solutions to minimize false positives, combining engineering, statistics, and technology:
- Statistical definition of realistic tolerances (based on Cpk/Ppk and standard deviation)
- Implementation of automatic repeatability tests in TestStand
- Robust and well-connected test jigs (with contact sensors, presence verification)
- Tools for real-time diagnostics (cameras, redundant sensors)
- Dashboards with indicators of FPY, failure rates, rejection causes
- Cross-validation between test stations to confirm failures
✅ Best practices to reduce false positives
- Calibrate instruments and validate jigs with Reference Unit (Golden Unit)
- Perform automatic repeat tests for unexpected rejections
- Avoid tight test limits without statistical justification
- Eliminate external interferences (vibration, electrical noise)
- Invest in intelligent and reliable functional tests
Reducing false positives is not just a matter of accuracy, but also of efficiency, economy, and confidence in quality. AJOLLY Testing helps you reject only what really needs to be rejected.