Probability Formula

Formulae for Probability

Works for All Cases:

  1. P(A∪B)=P(A)+P(B)-P(A∩B)

  2. P(A|B)=\displaystyle\frac{P(A\cap B)}{P(B)}

  3. P(A’)=1-P(A)


For Mutually Exclusive Events Only:

  1. P(A∩B)=0

Mutually Exclusive
Mutually Exclusive


For Independent Events Only:

  1. P(A∩B)=P(A) P(B)

  2. P(A|B)=P(A)

  3. P(B|A)=P(B)

  4. P(A’∩B)=P(A’) P(B)

  5. P(A∩B’)=P(A) P(B’)

  6. P(A’∩B’)=P(A’) P(B’)