Illustrations of the Logic of Science

An Interactive  version of Peirce's 1878 paper on probability theory and scientific inference. 

Sections of text highlighted in blue can be clicked to show an interactive example of the point being made in that paragraph. 

An app for exploring Signal Detection Theory, N-P hypothesis testing, and Severity. 

In 1884, Peirce published "A Numerical Measure for the Success of Predictions".  Earlier that year, Sgt. Finley devised a method for predicting tornadoes, and scored his method favourably. He gave it a 96% as he was right 96% of the time.  

Peirce and others responded by noting that most of Finley's  success was due to the fact that tornadoes are rare.  Finely would have gotten a better score (98%) by simply always saying "No Tornado". 

Peirce offered an alternative way to assess such methods. The score, which he called "the science of the method" is now called The Peirce Skill Score, among other things. 

(Image from Finley's booklet)