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Counterexample

Is this true?

Pairwise independent events are mutually independent

No — it is false.

The counterexample

Two fair coin tosses: A = first is heads, B = second is heads, C = the two agree

Why it fails

Each pair is independent, but P(A∩B∩C) = 1/4 ≠ 1/8 = P(A)P(B)P(C).

Go deeper· Explained in full in Probability axioms, conditioning and independence· Asked in CSIR NET December 2025· From Probability › Axioms, conditional probability, independence, Bayes

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