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LECTURE 10
Probability: An Introduction
> Probability is used as a mathematical tool to understand or describe random
phenomena, chance variation and uncertainty
>Applications: genetics; quality control; finance, etc
Basic Concepts
>Probability is used as a model/tell for situations for which outcomes occur randomly
>such situations are called
experiments
, and the set of all possible outcomes is called
the
sample space
>A
simple event
is the outcome of a single repetition of a random experiment
>One and only one simple event can occur when an experiment is performed once
>One can
assign a probability
to each simple event in the sample space
>The set of all possible events of an experiment is called the
sample space (usually
denoted by S)
corresponding to that experiment
>An
event (usually denoted by E, F, A, B, etc)
is a collection of simple events. In
another words, a subset of the sample space.
>Any subset of the sample space (including the empty set) is an event
>Two events are
mutually exclusive
if whenever one of them occurs and the other
cannot occur
Probability: Relative Frequency View
>How often does "an event" occur?
Relative frequency = f/n
>As sample size n becomes "large"
Relative frequency becomes better indication of probability
Probability of an Event: Properties
>Probability of an event is a number between 0 and 1
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This note was uploaded on 01/17/2011 for the course PSC 123 taught by Professor Roth during the Spring '10 term at San Diego.
 Spring '10
 Roth

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