9/26/2009
1
Random Variables and
Discrete probability
Chapter 7
Distributions
7.2 Random Variables and Probability Distributions
A random variable is a function or rule that
assigns a numerical value to each simple event
in a sample space.
A random variable reflects the aspect of a
random experiment that is of interest for us.
There are two types of random variables:
Discrete random variable
Continuous random variable.
A random variable is discrete if it can assume a
countable number of values.
A random variable is continuous if it can assume an
uncountable number of values.
Continuous random variable
Discrete random variable
Discrete and Continuous Random Variables
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After the first value is defined
the second value, and any value
thereafter are known.
Therefore, the number of
values is countable
After the first value is defined,
any number can be the next one
Therefore, the number of
values is uncountable
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