You start with some initial belief, usually called your…
You start with some initial belief, usually called your prior probability or base rate: Initial (Prior) Probability = Base Rate Then, you update your estimated probability based on the evidence or information at hand. You can do this by multiplying your initial probability by an evidence factor: Updated Probability = Base Rate Evidence Factor
— from Decisions & Choices (Decision/Choice/Focus/Forethought/Consequences) · Practical Uncertainty: Useful Ideas in Decision-Making, Risk, Randomness, and AI by Hossei
In the book
How good is the best case — and how bad is the worst, and could I get back here if it came true? And the one I lean on most: how much will this even matter in five years? When the outcome is truly uncertain, stop pretending you can know it and think in probabilities instead: start from the base rate, the plain odds, and revise as each new fact arrives; hold many possible outcomes in mind, not just the one you hope for; and play each alternative forward in your mind, to its end, before you choose. A few simple habits sharpen all of this. — Decisions & Choices (Decision/Choice/Focus/Forethought/Consequences)