The decisions we make in life often come down to Bayes' Theorem, but most of us don't even realise what it is. So how does it work?
Our world view and resultant actions are often driven by a simple theorem, devised in secret more than 150 years ago by a quiet English mathematician and theologian, Thomas Bayes, and only published after his death.
Bayes’ Theorem was famously used to crack the Nazi Enigma code during World War II, and now manages uncertainty across science, technology, medicine and much more.
Bayes’ Theorem explained
Thomas Bayes’ insight was remarkably simple. The probability of a hypothesis being true depends on two criteria:
how sensible it is, based on current knowledge (the “prior”)
how well it fits new evidence.
Yet, for 100 years after his death, scientists typically evaluated their hypotheses against only the new evidence. This is the traditional hypothesis-testing (or frequentist) approach that most of us are taught in science class.
The difference between the Bayesian and frequentist approaches is starkest when an implausible explanation perfectly fits a piece of new evidence.
Let me concoct the hypothesis: “The Moon is made of cheese.”
“Nice guys finish last” is one of the most widely believed maxims of dating. Fleshed out, the idea goes something like this: heterosexual women might say they want nice characteristics in a partner, but in reality what they want is the challenge that comes with dating a “bad boy”. This idea is so widespread that some people are even making money off the back of it, selling self-help books and teaching men how to pick up women by insulting them – a practice known as “negging”.
Recently, an article published by Broadly claimed, “Everyone knows … are desirable. Thanks to a recent study, this is now scientifically verifiable.”
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