http://www.ck12.org Chapter 4. Discrete Probability Distribution
4.2 Probability Distribution for a Discrete Random Variable
dom Variable
Learning Objectives
- Know and understand the notion of discrete random variables.
- Learn how to use discrete random variables to solve probabilities of outcomes.
Now, we want to specify the possible values that a discrete random variable can assume. The example below
illustrates how.
Example:
Suppose you simultaneously toss two fair coins. Letxbe the number of heads observed. Find the probability
associated with each value of the random variablex.
Solution:
Since there are two coins and each coin can be either heads or tails, there are four possible outcomes(HH,HT,T H,T T)
each with probability 1/4. Sincexis the number of heads observed, thenx= 0 , 1 ,2. The Venn diagram below shows
the two-coin experiment.
From the Venn diagram, we can identify the probabilities of the simple events associated with each value ofx: