This document defines common probability symbols and concepts including: the symbols for 'OR', 'AND', and 'NOT' events as well as conditional probability; the formulas for calculating probability of unions, intersections, complements; and the relationships between independent and mutually exclusive events. Conditional probability is calculated by reducing the sample size to only cases where the condition is true. Independent events have a probability of intersection that is the product of their individual probabilities, while mutually exclusive events cannot occur together so their union probability is the sum of individual probabilities minus the intersection.

1. "OR" event symbol U
"AND" event symbol n
"NOT" event symbol '
"GIVEN" event symbol /
P(AUB) Probability that outcome is in event A or B or both
P(AnB) Probability that outcome is in both A and B
P(A') Probability of all outcomes that are not in A
P(A/B) Probability that A will occur given that B has already occurred
Conditional probability (given, /) reduces the sample size, so calculate with a
reduced sample size
Formula for conditional (given, /) P(A/B)= P(AnB) / P(B)
Independent variable the fact that A occurs does not effect the probability that B
will occur
Independent variable formula P(AnB)=P(A)*P(B)
Mutually exclusive event ("disjoint") events that cannot occur at the same time
Intersect formula for independent variables P(AnB)=P(A)*P(B/A)
Union formula for mutual events P(AuB)=P(A)+P(B)-P(An)
General multiplication rule P(AnB)=P(A)*P(B/A) OR P(AnB)=P(B)*P(A/B)