AP Statistics Section 6.3C More Conditional Probability

1. AP Statistics Section 6.3CMore Conditional Probability

2. Recall that the conditional probability of B, given A, is:

3. Example: Use the table from the last page of notes to determine the conditional probability that a grade at the university is an A, given that it comes from a liberal arts course.L = grade from a liberal arts course A = grade of AP(L) = P(Land A) = P(A| L) =

4. The intersection of any collection of events is the event that ___ of the events occur. all

5. The extended multiplication rule looks like this:

6. Example: Only 5% of male high school basketball, baseball and football players go on to play at the college level. Of these, only 1.7% enter major league professional sports. About 40% of the athletes who compete in college and then reach the pros have a career of more than 3 years. Define the events as follows: A= {competes in college} B= {competes professionally given they played in college}C= {pro career longer than 3 years given they played in college and then went on to the pros}What is the probability that a high school athlete competes in college and then goes on to have a pro career of more than 3 years?

7. Example: Online chat rooms are dominated by the young. Teens are the biggest users. If we look only at adult internet users (aged 18 and older), 47% of the 18 to 29 age group chat, as do 21% of those aged 30 to 49 and just 7% of those 50 and over. To learn what percent of all adult internet users participate in chat rooms, we also need the age breakdown of users: 29% of adult users are aged 18 to 29, 47% are aged 30 to 49 and 24% are 50 and over. We will use a tree diagram to organize our thinking.

9. What percent of all adult internet users take part in chat rooms?

10. What percent of adult chat room users are between 18 and 29 years old?

11. Are the events “18-29 year old internet user” and “adult chat room user” independent”?