Result vs Limit Check: Conformity Decisions for Test Results
What is the Result vs Limit Check?
Test results carry measurement uncertainty, so directly comparing a result with a limit near the boundary can lead to wrong conformity decisions. The scientifically sound approach, for example ISO 10576 and CNAS-GL015, includes the uncertainty in the decision: the conclusion is reliable when result + U is still below an upper limit (or result − U still above a lower limit), and "not determined" when the result falls inside the uncertainty band, requiring retesting or improved measurement. Uncertainty-inclusive decisions control both producer and user risk.
When to Use It
Use it whenever a measured result must be judged against a standard limit: physicochemical and microbiological testing, batch release, environmental monitoring and food compliance. It is also useful for comparing inspection data with specification limits in quality laboratories. For multiple indicators, each is judged separately and the strictest result decides the overall verdict.
How to Use It (Step by Step)
Select the limit type (upper, lower or interval), enter the limit value and the expanded uncertainty U, then enter one or many test results. The tool applies the rules row by row, returns pass, fail or inconclusive for each, and summarizes the batch. If uncertainty data are unavailable, use simple direct comparison but stay cautious near the limit, or estimate U with the uncertainty tool first.
Key Formulas / Example
For an upper limit: pass if result + U ≤ limit; fail if result − U > limit; otherwise inconclusive. For example, with a limit of ≤ 10, a result of 9.8 and U = 0.5, result + U = 10.3 exceeds 10, so the verdict is inconclusive and a retest is recommended.