1. Chapter 9 Section 1
Probability Review

2. Probability Review .25 25% .2857 28.6% 100% 1 Fraction Decimal Percent
1. ¼
2. 2/7
3. 1
.25
25%
.2857
28.6%
100% 1
Probability
How likely it is that an event
will occur

3. Vocabulary Theoretical Probability P(E) = # of favorable outcomes
What “should” happen, mathematically
P(E) = # of favorable outcomes
# of total possible outcomes

4. More Vocabulary Trials Outcomes Results of the trials
Each time an experiment is performed
Outcomes
Results of the trials
Experimental Probability
Found by actually observing an experiment
(what really happened)

5. Ex. 1 What is the probability of rolling a 6 on a die?
P(E) = # of favorable outcomes
# of total possible outcomes
Ex. 1 What is the probability of rolling a 6 on a die? 1
P(6)= 6
Ex Out of 1100 people, 836 played a sport. What is the probability that a person picked at random will play a sport?
836 =
19/25
P(play a sport)=
1100

6. How to find a sample space:
The set of all possible outcomes of an experiment
How to find a sample space: 1 2 3 4 5 6 H1 H2 H3 H4 H5 H6
Tree Diagram H
Draw a tree diagram to show the sample space of flipping a coin and then rolling a 6-sided die.
12 possibilities!!! 1 2 3 4 5 6 T1 T2 T3 T4 T5 T6 T

7. Ex. 3 A person flips a penny, a nickel and a dime
Ex. 3 A person flips a penny, a nickel and a dime. Find the probability that EXACTLY 2 of the coins landed on heads? H T
HHH H T
P(exactly 2 heads)=
HHT H H T
HTH
= 3
HTT 8 H T
THH H T
THT T H T
TTH
TTT

8. Ex. 4 Suppose a coin is flipped 100 times, Predict how many time you will roll a heads.
P(heads)= 2
½ of 100 
½(100)= 50