9-7 Independent and
Dependent Events
(pg. 398-401)
Indicator: D7
• Compound event- 2 (or more) simple
events
• Independent events – The outcome of
the first event does not effect the outcome
of the next event. P(A&B)= P(A)•P(B)
Example:
P (rolling “5” and tails)=
1
1 1
 
6 2 12
Dependent Events- the outcome of
one of the events affects the
outcomes of another event.
P(A & B)=P(A)• P(B following A)
Example:
P (queen and 3)= 4  4  16

52 51 2652
4
or 0.6%
663
You Try
1) Tossing 4 coins and getting heads on all
four?
2) There are 10 country CD’s and 15 rock
CD’s. What is the probability of drawing
a rock then a country CD?
• Mutually Exclusive events: Can not
happen at the same time
P(A or B) = P(A) + P(B)
2
1
1
P(2 or 3 on a dice)=
 
6 6 6
or
1
3
Homework
• Period 3--> 9- 7 page 400-401 #1719 & 22-32 all