Probability Notes

Question – Explain addition theorem in probability.

Addition Theorem in Probability : As n (Ø) = 0, it follows that P(Ø) = 0.

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By definition, P(X) =

n(X) = 1. n(X)

If A and B are two events, then n(A ∪ B) = n (A) + n (B) + n (A ∩ B). Therefore, P (A ∩ B) = P (A) + P (B)  – P(A ∩ B).

If A and B are two mutually exclusive events, then the probability of their union is the sum of the probabilities of A and

B. i.e., if A ∩ B = ∅, then P (AB) = P (A) + P (B).