 Risk is the lack of certainty about the outcome of making a particular choice.Statistically, the level of downside risk can be calculated as the product of the probability that harm occurs (e.g., that an accident happens) multiplied by the severity of that harm (i.e., the average amount of harm or more conservatively the maximum credible amount of harm).In practice, the risk matrix is a useful approach where either the probability or the harm severity cannot be estimated with accuracy and precision.