Tree Diagrams and Conditional Probability

Section 11 - 4: Conditional Probability

GOAL: To be able to find conditional probability using tables and/or tree diagrams.

Multiple Choice

The table is the results of a survey about favorite sport to watch on TV. What is the probability that a person chosen at random would prefer football given they are a female.

• 2/25

• 3/13

• 12/73

• 26/75

Conditional Probability

The probability that an event, B, will occur given that another event, A, has already occurred. For the previous question; given they are a female...how many females? This is the "out of." Of those females how many prefer football?

Let's try it...

• Probability of randomly selecting a person who is a male given they prefer baseball?

• Prefer Baseball (the "out of") = 60. Males who prefer baseball (what you want) = 15.

• The probability would be 1/4 or .25 or 25%

Multiple Choice

Chelsea surveyed a sample of students in the senior class to determine the distribution of students with a drivers' license. The results are in the table. What is the probability of selecting a student at random that is a female?

• 1/2

• 11/20

• 1/4

• 11/40

Multiple Choice

Find the probability that a person selected at random is a male given they have no license.

• 1/2

• 5/8

• 3/4

• 1/3

Multiple Choice

Find the probability that a student chosen at random has a Learner's Permit given they are a female.

• 5/8

• 1/2

• 1/4

• 3/5

Break down the Chart Further

• College Degree of No College Degree

• Voted or Did Not Vote

• With conditional probability you simply follow the branches.