CV × 1.96 calculator
Imprecision-based uncertainty at 95% CI
CV% × 1.96 is a simplified way of estimating uncertainty from random error (imprecision) only at approximately 95% confidence.

Formula: U = 1.96 × CV%

Example: If CV% = 2.0%, then U = 1.96 × 2.0 = 3.92%
This means results vary by approximately ±3.92% around the true value at 95% confidence.

Note: This estimates imprecision-based expanded uncertainty only. Full ISO 15189:2022 MU also incorporates bias: k × √(CV² + Bias²)
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Enter your mean value and CV%, then click Calculate U = 1.96 × CV% to see imprecision-based expanded uncertainty.
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Interpretation guide
Based on relative expanded uncertainty (%U)
✓
Low Uncertainty — %U ≤ 5%
Measurement uncertainty is within acceptable limits. Results can be reported with high confidence. Routine QC monitoring is sufficient. Suitable for all clinical decision thresholds.
⚠
Moderate Uncertainty — 5% < %U ≤ 10%
Acceptable in most routine clinical contexts. Consider reviewing imprecision and bias sources. Monitor trends in QC data. Results near clinical decision limits should be interpreted with caution.
✕
High Uncertainty — %U > 10%
Uncertainty exceeds typical laboratory quality goals. Investigate root causes — check calibration, reagent lot stability, analyst technique, and instrument performance. Results require clinical context. Consider corrective action before reporting.
ISO 15189:2022 key clauses
Relevant MU requirements
Clause Requirement
7.3.3Laboratory shall determine MU for each examination
7.3.3 b)MU shall be estimated with k=2 unless otherwise justified
7.3.3 c)MU shall be evaluated at medically relevant concentrations
7.3.3 d)MU shall be reviewed if analytical performance changes
7.4.1.2MU shall be reported on request; available to users