View source for Probability Formulas - Rhea

The opposite or complement of an event A is(that is, the event of A not occurring)is

    <math>P(A') = 1 - P(A)\,</math>

If two events, A and B are independent then the joint probability is

    <math>P(A \mbox{ and }B) =  P(A \cap B) = P(A) P(B)\,</math>

If two events are mutually exclusive then the probability of either occurring is 

    <math>P(A\mbox{ or }B) =  P(A \cup B)= P(A) + P(B)</math>

If the events are not mutually exclusive then

    <math>\mathrm{P}\left(A \hbox{ or } B\right)=\mathrm{P}\left(A\right)+\mathrm{P}\left(B\right)-\mathrm{P}\left(A \mbox{ and } B\right)</math>

Conditional probability is written ''P''(''A''|''B''), and is read "the probability of ''A'', given ''B''".

    <math>P(A \mid B) = \frac{P(A \cap B)}{P(B)}\,</math>