ISO 14971 risk thinking: a practical severity and probability matrix

ISO 14971 leaves the scales and what counts as acceptable to your own policy. A 5 by 5 severity by probability grid is a useful view in a design review, as long as the real criteria live in the risk management plan.

Worked example. A false negative on a critical marker. Severity 4 (critical), probability 2 (remote), score 8. Controls: better signal checks, a human-factors step that catches use error, and a verification that sensitivity holds. Residual risk is rescored 4 by 1.

Common mistakes. Treating the score as something the standard requires. Using a warning as the first fix when a design change is feasible. Leaving use-related hazards out of the same file.

Sketch the risks: https://nexamedtech.com/tools/iso-14971-risk-matrix