Conditional Probability Tree
Visualize a two-event probability tree. Set P(A), P(B|A), P(B|¬A) and see joint, marginal, and posterior probabilities with a labeled diagram.
Inputs
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Probability tree
Result
Why probability trees matter
Most probability questions confusion comes from confusing P(A|B) with P(B|A). A tree makes the order of multiplication explicit and the law of total probability (P(B) = P(B|A)·P(A) + P(B|¬A)·P(¬A)) becomes a visual sum of two branches.
Who uses it
- Educators teaching the law of total probability.
- Medical residents internalizing sensitivity/specificity.
- Engineers working through reliability block diagrams.
Limitations
- Two events only. For three+ events, the tree grows exponentially — try the Bayes calculator instead.
- For very small probabilities, canvas text becomes hard to read — interpret numerically.