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Chapter
5
Discrete Random
Variables and Their
Probability Distributions
Mean and Standard Deviation of a Discrete Random Variable
Computing the mean and standard deviation of a discrete random variable is slightly different
than computing the mean and standard deviation of a set of data values. Each data value in the
data set weighs equally in the computation. In a discrete random variable the possible data
values are given along with the likelihood of each value occurring on any given single trial. For
example:
Value (x) Probability P(x)
0 .2
1 .3
2 .4
3 .1
The TI-83, TI-83 Plus, and TI-84 Plus calculators allow you to input the values and their
probabilities into separate lists and use the 1-Var Stats function to compute the descriptive
statistics.
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