Chapter 6
Discrete
Probability
Distributions
Section 6.1
Probability
Distributions
In Chapter 5, we presented the concept of an experiment and the outcomes
of an experiment. When experiments are conducted in a way such that the
outcome is a numerical result, we say the outcome is a random variable.
A random variable is a numerical measure of the outcome of a probability
experiment, so its value is determined by chance. Random variables are
denoted using capital letters such as X. Each of the observed values are
denoted with a small letter such as x.
A discrete random variable is a random variable that has either a finite
number of possible values or a countable number of possible values.
A continuous random variable is a random variable that has an infinite
number of possible values that is not countable.
The probability distribution of a random variable X provides the possible
values of the random variable and their corresponding probabilities. A
probability distribution can be in the form of a table, graph, or mathematical
formula.
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