Probability

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Probability Basics

Definitions and Examples

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Probability Definition

Probability is a way of measuring the likelihood or chance of the occurrence of outcomes of a procedure. Probabilities are measured as values ranging from 0 to 1, with a probability of 0 indicating an impossible event (one that could never occur), a probability of 1 indicating an event that is certain to occur (will definitely, or always happen), and probabilities in between indicating events that could possibly occur - values closer to 0 indicating less likely events, closer to 1 indicating events that are more likely.

Terminology and Notation

P(E)

Event

Sample Space

represents the probability of event E (or any other event that we want to describe can go in those parentheses). P(E)= a number from 0 to 1 (0≤P(E)≤1)

the set of all possible outcomes of a procedure (usually called S)

a collection of some of the possible outcomes from the sample space (usually labeled with other capital letters – A,B,C,…)