Risk is often the most important element to consider in a big decision. It is certainly the area that causes the most anxiety. But a lot of people and organisations have problems dealing with it, and usually this starts with the words they use.

You might hear a co-worker say something like, “Such and such an event will probably happen.” Behind this statement, one assumes, is some sense of probability in the head of the speaker, but what does “probably” mean? It might vary according to the speaker, whether he is an optimist or a pessimist, and maybe also the nature of the event, whether it is “good” or “bad”. What is the lowest probability you would attach to the event? What is the highest?

Now substitute some different words. What range of probability would you attach to these words?

• Possibly
• Likely
• Unlikely
• Certainly

I use this discussion with client groups to introduce the topic of assessing risk. Collecting the ranges from the individuals in the room, it doesn’t take long to discover that the words can mean almost anything. Different people’s ranges—for the same word—can span a very large fraction of the space between 0.0 and 1.0, sometimes for some words even the entire space!

It also doesn’t take long to discover that there are two people in the room who—for the same word—have ranges that do not even overlap! Imagine these two talking to each other about an important assessment. Any true meaning in their communication will just pass them by...

The best way to communicate about uncertainty is to use the language of probability and to assess probabilities as numbers. Using probabilities reduces ambiguity. We may disagree about whether the chance of an event is 0.7 or not, but I hope we would not disagree about what a probability of 0.7 actually means. Your listener understands you, and your basis for judgment is communicated.

When it comes to risk, use numbers, not words.