Based on actual past returns, then, there is a 99.73% probability of the S&P 500 being within a much wider range of 890 and 3790. The Difference Between a Prediction and a Probability ...

Can someone truly be lucky or are life events just random? Statistician Jeffrey Rosenthal untangles the meaning behind luck, chance, fate and magic in his new book, Knock on Wood.

This is really a probability only in the sense of drawing names from a hat. It also applies unevenly across the population – say, due to differences in driving behavior and local road conditions.

Unlike possibility, the ‘Probability’ is more data-driven and an intelligent way of assessing the chances of something happening. Probability can range from 0% to 100%.