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Data & Analytics · Intermediate

Conditional Probability

The probability of an event given that another event has occurred: P(A|B) = P(A and B) / P(B).

Definition

If A and B are independent, then P(A|B) = P(A). Conditional probabilities underpin funnels, risk scoring and Bayesian reasoning.

Example

P(purchase | added to cart) = 0.4

Exam tip

P(A|B) ≠ P(B|A); confusing the two is the prosecutor's fallacy.

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