How to convert P values into REAL probabilities

As part of the EBM 2.0 project, a supplementary explanatory page has been released explaining how to convert p values into the actual probability that a finding is real.

This goes to the heart of the longstanding misinterpretation of the p value – the incorrect related beliefs that the p value represents the probability that the null hypothesis is false and therefore 1 minus the p value tells you the probability that the evaluated therapy (main alternate hypothesis) is true.

Instead, p values effectively function as likelihood ratios converting pre-test probabilities into post-test probabilities (where the study is the “test”), generally resulting in far lower probabilities of published study findings being true than we had previously thought.