## 13.1 Outline

- Terminology
- experiment
- sample space
- event
- definition
- impossible event
- simple event
- mutually exclusive

- die
- equally likely outcomes
- sample space

- Probability
- probabilistic model
- relative frequency
- types of
- empirical probabilities (a posteriori)
- theoretical probabilities (a priori)
- subjective probabilities

- law of large numbers
- definition
- sample space for a pair of dice
- finding probabilities by counting

- Probabilities of unions and intersections

## 13.1 Essential Ideas

If an experiment can result in any of *n *mutually exclusive and equally likely outcomes, and if *s *of those outcomes are considered favorable, then the probability of an event *E*, denoted by *P *(*E *), is *P*(*E *) =*s/n.*

Procedure for finding probability by counting:

- Describe and identify the sample space,
*S*. The number of elements in*S*is*n*. - Count the number of occurrences that satisfy the event of concern; this is the number of successes,
*s*. - Compute the probability of the event using the formula
*P*(*E*) =*s/n.*