Risk: probability and outcome

One way of thinking about risk is in terms of the probability of one or more outcomes. Probability provides a way of using knowledge derived from the observation of past events to predict the likelihood of similar outcomes in the future. There is a strong technical and objective reality to probability; it is often expressed numerically. In contrast, outcomes are more subjective and relate to personal and collective values.

This difference can be seen in gambling. When individuals choose to bet on a horse race, they are taking a risk. If their horse loses, they lose their stake, but if their horse wins, they win. The size of their winnings depends on the horse's ‘odds’, that is, the probability of the horse winning based mainly on evidence from previous races. The choices individuals make depend on their personal preferences and values. If they value certainty, they will not bet. This means that they can be sure they will not lose money, but they will forego the chance of winning and the excitement of betting. If they value risk-taking and the chance to make a big win, then they will back a ‘long shot’.

When choices are made on behalf of others and the outcomes affect different social groups, it is no longer just a matter of personal preference but one of collective values. This can be seen in the process of triaging, a way of prioritising and allocating scarce resources, for example following a battle or disaster or in hospital accident and emergency units.

Triaging was developed during the Napoleonic Wars (1803– 1815) by the French military surgeon Dominique Jean Larrey to minimise deaths (Skandalakis et al, 2006). In the battlefield setting, it involves categorising the injured and allocating resources between three main risk categories:

• Category 1 No active treatment for the most seriously injured (low probability of survival);

• Category 2 Immediate treatment for the seriously injured (good chance of survival with treatment);

• Category 3 Delayed treatment for those who have minor injuries (near certainty of survival).