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).
Number of possible outcomes  
Number of event occurs in A  
Number of event occurs in B  
Note: A & B are mutually exclusive events  


P(A)  P(A')  
P(B)  P(B' )  
P(A ∩ B)  P(A ∪ B)  
P(A  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') = 10.2 = 0.8
 P(B) = 5/50 = 0.1
 P(B') = 10.1 = 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