Lesson 5.1 – Introduction to Random Variables

  • Verify that the probability distribution of a discrete random variable is valid.
  • Calculate probabilities involving a discrete random variable.
  • Classify a random variable as discrete or continuous.


Activity: How many siblings to you have?

Students start by each putting a tally mark next to the number of siblings in their family.  Be sure to tell them to include themselves and count any step-siblings or half-siblings.  As a class we found the probability for each X value by writing each total as a fraction over the class size.  Using their knowledge from Chapter 4, students should be able to work through the entire Activity in small groups.




Students have experience with the first two learning targets from Chapter 4.  The new big idea in this lesson is discrete versus continuous variables.  Our class decided that values for discrete random variable “have gaps” and that “certain decimals do not make sense”, while for continuous there are “no gaps and decimals are OK”.  Lessons 5.2, 5.3 and 5.4 are dealing with discrete random variables, and lessons 5.5, 5.6, and 5.7 are dealing with continuous random variables.


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