8.3 Disjoint Events
Disjoint Events
Disjoint events are events that cannot happen at the same
time.
Some examples:
 Getting heads and getting tails on a coin toss
 Rolling a 5 and rolling a 2 on a number cube
 Winning a contest and not winning a contest
Overlapping events
Overlapping events are events that could happen at the
same time
Some examples:
 Rolling an even number and rolling a 2
 Choosing a fiction book and choosing a Harry Potter
book
 Winning a car and winning a iPod
Event R: _________________________
Event S: 2, 3, 7
Disjoint or overlapping? Explain: ________________________________________________
_________________________________________________________________
***To find the probability of two disjoint events…ADD their probabilities!!
Not sure if it is a disjoint event? Look for the word “or”!
Guided Practice (Use with Example 2):
___________ + ___________ = ___________
Complementary events are two disjoint events when one or the other must occur. For example, when flipping a coin you
must get either heads or tails, so “getting heads” and “getting tails” are complementary events.
***The probably of disjoint events that are complementary always add up to 1.***
Guided Practice (use with example 3):
First, find the percent that does not have a briefcase: 100% - ___________ = ___________
Next, using this percent, get the number out of 350 riders that would probably not have a briefcase. Use a proportion or
multiply!
8.4 Compound Events
A Compound event is an event that is made of two or more events that can happen at the same time or one after the other.
Use a table or tree diagram to organize these events.