International – Estimating the likelihood of a use error: Part 1

In mathematical terms, risk is the number you get when you multiply the values assigned to the likelihood of a use error resulting in harm (A), and the severity of that potential harm (B). The product of (A x B) is often referred to as the risk prioritization number (RPN). For example, say you are rating likelihood and severity on 5-point scales, as is common practice in risk management. The likelihood of a use error resulting in harm could range from 1 = Rare to 5 = Almost Certain. The severity of that harm could range from 1 = Negligible to 5 = Catastrophic. If a use error was considered Likely to Occur (likelihood = 4) and capable of causing Moderate harm (severity = 3), the RPN would be (4 x 3) = 12. Depending on your organization’s risk management procedure, this could (and probably does) indicate the need to implement risk control measures (i.e., mitigations)…