Conditional Probability

Objective:I can find the probability of a

conditional event.

Conditional Probability

Probability of event A, given event B occurs.Notation: P(A|B)

Two machines produce optical lenses.Machine 1: 6 defects out of 200 lenses made.Machine 2: 5 defects out of 250 lenses made.

Probability of getting a defective lens.

P(defective lens) =

P(defective lens | Machine 1)

Probability of getting a defective lens if it is made from Machine 1.

11450

=0.024=2.4 %

¿6

200=0.03=3%

What does the above notation mean?

Complement of an event: All other possible outcomes.

What is the complement?

1. “Heads” when tossing a coin.

2. “Winning” a game

3. “The door is open”

4. “Red” for a traffic light

5. “Rolling an even #”

“tails”

“losing”

“The door is closed”

“Green or yellow” light

“rolling an odd #”

Events A and B are complements then P(A) + P(B) =1

Assignment: section 14.2

Pg 502-503: 1-7

Pg 238 12-26 even and 27,28