I regularly write about the fun to be found in probability and statistics - but also the difficulties we face in understanding them, because our brains don't seem to be wired in a way that adequately deals with this kind of mathematics. However, there's one misunderstanding that stands out heads and shoulders above the rest - and this is that we find it very difficult to distinguish between forecasts and facts. Data about past events can be (though isn't necessarily) accurate. Data about the future is often only accurate if you are lucky. I'm not saying all forecasting is worthless - it's the best of a set of bad options (certainly better than relying on Mystic Meg) - but we always need to be aware of its limitations. Let's take a simple personal example. My mortgage will soon be coming off a fixed rate, and the bank has kindly offered me a series of options for new fixed-rate details. To be able to decide between them, whether consciously or not, I have t...