Tuesday, July 13, 2010

Round in circles









David Spiegelhalter, professor for the public understanding of risk, had a nicely wry & funny article in The Times on Friday about Paul, the octopus who foretold the result of World Cup football matches. You can read it for free here on the Understanding Uncertainty blog.

Unfortunately the professor adds a rider that did not appear in the newspaper: ‘Even if Paul's final two predictions are correct, it does not change my total belief that he is not psychic and the results are just chance. Essentially when a hypothesis has zero initial probability, no amount of surprising evidence will shift that belief.’

Now does this not rather give the game away?

If my total belief is that there is no such thing as man made global warming, then no amount of evidence scientists produce will shift that belief.

And vice versa.

So then the problem becomes one of how do we change belief.