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Probability Calculator.

Single Probability Calculator

Formulas:

  • Probability of event A occurring P(A) = n(A) / n(S).
  • Probability of event A not occurring P(A') = 1 - P(A).


Multiple Event Probability Calculator

Formulas:

  • Probability of event A occurring P(A) = n(A) / n(S).
  • Probability of event A not occurring P(A') = 1 - P(A).
  • Probability of event B occurring P(B) = n(B) / n(S).
  • Probability of event B not occurring P(B') = 1 - P(B).
  • Probability of both events occurring P(A ∩ B) = P(A) x P(B).
  • Probability of either events occurring P(A ∪ B) = P(A) + P(B) - P(A ∩ B).
  • Conditional Probability P(A | B) = P(A ∩ B) / P(B).


Example Multiple Probability Calculation

Find multiple event probabilitiy, given n(s) = 50, n(A) = 10 and n(B) = 5

P(A) = 10/50 = 0.2

P(A') = 1-0.2 = 0.8

P(B) = 5/50 = 0.1

P(B') = 1-0.1 = 0.9

P(A ∩ B) = 0.2 *0.1 = 0.02

P(A ∪ B) = ( 0.2 + 0.1 ) - 0.02 = 0.28

P(A | B) = 0.02 / 0.1 = 0.2