What is it
A-Level probability extends GCSE work to conditional probability notation (like P(A|B)), and to formally testing whether two events are independent using the multiplication rule.
Why it matters
Conditional probability is the mathematical foundation behind real decision-making under uncertainty — medical testing, spam filtering, risk assessment — all rely on exactly this reasoning, formalised with precise notation.
Exam tip
Learn to translate word problems into set notation (P(A∩B), P(A∪B), P(A|B)) before attempting to calculate — misreading which probability is actually being asked for is a more common error than any calculation mistake.
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