Conditional Probability: the likelihood that an event will occur GIVEN that another event has already occurred. A two way table & tree diagrams can represent these types of events. The probability of event B given event A has occurred is represented as P(B|A) Example: P(18 to 24|female) = 5668/9321 ≈

1) What is the probability that a student chosen at random would be 35 years or older? 2) What is the probability that a student chosen at random would be 35 years or older given that they are female?

The intersection of events (events happening together) can be found as follows: P(A and B ) or P(A ∩ B) = P(A) * P(B|A) What if you want to determine if two variable events are independent of each other? Is age independent of gender? If P(B) = P(B|A), then the events are independent.

Are online chat rooms dominated by the young adults? Of all adult users... 29% are years (A 1 )47% are 30 – 49 years (A 2 ) 24% are 50+ years (A 3 ) 47% of the years use chat rooms 21% of the years use chat rooms 7% of the 50+ years use chat rooms What percent of adult chat room users are 18 – 29 years old?

Weekly Practice Pg 417 #33, 36 Pg 423 #37, 38 Pg 425 #44 Pg 430 #46, 48, 50 Pg 446 # 72 – 74 Pg. 453 # 86 Pg 455 #94