CK-12 Probability and Statistics - Advanced

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TABLE4.1:

Voter #1 Voter #2 Voter #3 Value of Random

Variable

(number of Yes

votes)

1 Y Y Y 3

2 Y Y N 2

3 Y N Y 2

4 N Y Y 2

5 Y N N 1

6 N Y N 1

7 N N Y 1

8 N N N 0

Figure:Possible outcomes of the random variable in this example from three voters.

In the light of this example, what do we mean by random variable? The adjectiverandommeans that the experiment
may result in one of several possible values of the variable. For example, if the experiment is to count the number
of customers who use the drive-up window in a fast-food restaurant between the hours of 8 AM and 11 AM, the
random variable here is the number of customers who drive up within the time interval. This number varies from
day to day, depending on random phenomena such as today’s weather among other things. Thus, we say that the
possible values of this random variable range from none( 0 )to a maximum number that the restaurant can handle.

There are two types of random variables,discrete and continuous.In this chapter, we will only describe and discuss
discrete random variables and the aspects that make them important for the study of statistics.