Bayesian Thinking for Everyday Decisions
Update beliefs with evidence step by step.
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Teach me to update a belief with evidence, using a decision of mine. The question: [QUESTION]. My prior belief with a rough probability: [PRIOR_BELIEF]. New evidence: [NEW_EVIDENCE]. How reliable that evidence is: [EVIDENCE_RELIABILITY].
Show the calculation with natural frequencies: imagine 1,000 situations like mine; how many fit my prior; how many of those would produce this evidence; how many of the others would produce it falsely; then the proportion of true cases among those showing the evidence. Provide the Bayes formula P(H|E) = P(E|H) x P(H) / P(E) with my numbers filled in.
Then: a table of how the answer changes if my prior or the evidence reliability changes (three values each); the base-rate neglect warning with an example; a statement of what would change my mind next; and the code for the update in 8 lines.
Finish with a plain-language sentence I could use ("Given what I know, I think there is about a 35 percent chance, and I will check X next"). Make clear that my prior is a judgment and give two ways to sanity-check it.
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