A Theoretical Approach
* Experimental probability is based on the observations of an experiment.
* Experimental probability gets closer to the theoretical probability as the number of observations increases.
* Theoretical probability of an event E,
P(E) = \frac{Number \thinspace \thinspace of \thinspace \thinspace outcomes \thinspace\thinspace \thinspace favourable \thinspace \thinspace to \thinspace \thinspace E}{Total \thinspace \thinspace number\thinspace \thinspace of \thinspace \thinspace possible \thinspace \thinspace outcomes }
* The possible outcomes of an experiment are called its elementary events.
* The sum of the probabilities of all elementary events of an experiment is always one.
* Two events that are mutually exclusive of each other are called complimentary events.
* The sum of probabilities of two complimentary events is always equal to one.
* An event having zero probability of occurrence is called an impossible event.
* An event having a probability of 1 is called a sure or certain event.