Odds Updater: Bayes’ Rule With Evidence Ratios

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Starting chance %

Clues to use

Clue 1: chance of it if true %

Chance of it if false %

Clue 2: chance of it if true %

Chance of it if false %

Clue 3: chance of it if true %

Chance of it if false %

Load an example from the book

Enter your numbers, then press Calculate.

From the book, Chapter 17. A 1% starting chance and a clue that shows up 95% of the time if true and 5% if false (evidence ratio 19): 16.1% after one clue, 78.5% after two independent clues, 98.6% after three. Starting at 0.1%: 1.9%, 26.5%, 87.3%. A witness right 80% of the time, about something 15% likely: 41.4%. A weak clue moves 10% only to 14.3%.

Multiply only for clues that can’t be wrong for the same reason; otherwise you count one clue twice. Everything stays in your browser: no sign-up, nothing stored or sent.