AP Sec 5.3 Conditional Probability

AP Sec 5.3 Conditional Probability

Independence and the Multiplication Rule

Conditional Probability

Calculating Conditional Probabilities

Open Ended

A survey of all residents in a large apartment complex reveals that 68% use Facebook, 28% use Instagram, and 25% do both. Write those three things using probability notation.

AP Exam Tip

You can use notation like P(A|B) if the events are defined in the problem. Otherwise, it's probably easier to use contextual labels like P(Instagram|Facebook) or P(I|F).

Independent Events IF:

• P(A|B) equals

• P(Anot B) equals

• P(A)

Poll

Is being a female independent of being right-handed?

• Yes, independent

• No, not independent

• Hmmm... is this a trick question?

Open Ended

To check for independence between two events check P(R|F) and P(R|not F) and P(R). Are being female and right-handed independent events? Show evidence for your response.

General Multiplication Rule

Learning Targets

• Conditional probability... P(A|B)=P(AandB)/P(B)

• Independence is when...P(A)=P(A|B)=P(A|B')

• General Multiplication rule...P(AandB)=P(A)*P(B|A)