3.1. Discrete Random Variables http://www.ck12.org
Looking at the data that resulted in this trial, there were 4 times of 20 that 5 heads appeared.
P(5 heads) = 204 or 20%.
Lesson Summary
Probability in this chapter focused on experiments with random variables or the numbers that you assign to the
probability of events. If we have a discrete random variable, then there are only a specific number of variables we
can choose from. For example, tossing a fair coin has a probability of success for heads = probability of success for
tails= 0 .50. Using tree diagrams or the formulaP=#o f favorable outcomestotal#o f outcomes , we can calculate the probabilities of these
events. Using the formula requires the use of the factorial function where numbers are multiplied in descending
order.
Points to Consider
- How is the calculator a useful tool for calculating probability in discrete random variable experiments?
- Are TREE Diagrams useful in interpreting the probability of simple events?
Vocabulary
Discrete Random Variables
Only have a specific (or finite) number of numerical values.Random Variable
A variable that takes on numerical values governed by a chance experiment.Factorial Function
(symbol: !) –The function of multiplying a series of descending natural numbers.Theoretical Probability
A probability calculated by analyzing a situation, rather than performing an experiment, given by the ratio of
the number of different ways an event can occur to the total number of equally likely outcomes possible. The
numerical measure of the likelihood that an event,E, will happen.P(E) =
number o f favorable outcomes
total number o f possible outcomes