Probability and conditional information

Probability and conditional information · Diagrams

Read a two-stage probability tree

Explore a probability tree

Choose outcomes, change conditional probabilities, and compare path products with event totals.

Multiply along a complete path; add disjoint complete paths. Each reached split totals 1. Second-stage probabilities are conditional on the first event.

Start branches to A and not-A with probabilitiesP(A),P(not-A). From A branch to B or not-B with conditional probabilitiesP(B|A),P(not-B|A); from not-A branch to B or not-B withP(B|not-A),P(not-B|not-A). Four leaf equations multiply the first probability by its conditional second-stage probability to give each intersection probability. Sibling alternatives are mutually exclusive and exhaustive.

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