Modern society relies on accurate statistics to help it function. However, we, as simple herd-based animals, just aren't equipped to accurately interpret the raw figures. Even simple things like being nervous of flying but happily travel at insane speeds in our cars, feeling comfortably cosseted and safe but in much more danger than hurtling through the air 7 miles above the surface of the Earth. For the nervous flyers here - you're more likely to die in the 3 mile taxi ride to the airport than on the 6000 mile flight to Hong Kong.

But such fears are sort of understandable and just need relatively simple statistics to be rationally understood. This entry is about a more sophisticated misunderstanding - the so called 'base rate fallacy'. Just how certain should we be of our modern systems? Is DNA evidence really totally infallible?

It's probably true today that after Bayes, given it's highly probable, then it's likely that something might not be at all usual. Or, to put it another way - Bayes' Rules

Back in the 18th century, Thomas Bayes started to look at the probability of something happening given some prior condition. His laws, rules or theorems have become really useful and important in the modern world. Issues like working out things how like a DNA match is to indicate guilt, how likely you really are to have a disease if you test positive in a test that is very accurate (but not perfect). If you've heard of the concepts of 'false positives' and 'false negatives' then Bayes will be your friend - I'm 97% positive about that!