Section 1
Probability and Odds
Vocabulary
probability: how likely it is an event will occur
experiment: taking a measurement or making
an observation
experimental probability: probability
determined by observation or measurement
outcome: result of each trial of an experiment
Experimental Probability
number of favorable observations of E
P( E ) 
total number of observations
• Probability is between 0 and 1.
• If probability is 0 then it is IMPOSSIBLE
for the event to occur
• If probability equals 1 then the event is
CERTAIN to occur
Ex 1
• Find the probability of rolling a number
greater than two on a die
Ex 2
• A class contains 6 students with black
hair, 8 with brown hair, 4 with blonde hair,
and 2 with red hair. Find P(black)
• Find P(red or brown)
• Find P(not blonde)
Ex 3
Lions fans
attending a
recent 3-game
series were
asked whether
the team should
have a mascot.
The table shows
the results of the
survey.
What is the
probability that
a Lions’ fan
wants a mascot?
Game
Attendance
In favor
of
mascot
Friday
681
527
928
388
428
786
Saturday
Sunday
Ex 4
A softball player has had 24 hits
in her first 60 times at bat.
Predict her number of hits in
330 at bats.
theoretical probability: the ratio of
favorable outcomes to the number
of possible outcomes in a sample
space
number of favorable outcomes
P(T ) 
number of possible outcomes
Experimental probability approaches
theoretical probability as more trials are
performed in an experiment.
Standard Card Deck
•
•
•
•
•
52 cards total
2 colors (red, black)
4 suits (hearts, diamonds, spades, clubs)
13 cards per suit (A,2,3,4,5,6,7,8,9,10,J,Q,K)
3 face cards per suit (J, Q, K)
Ex 5
A card is picked at random from a standard deck of
52 cards. Find P(face card).
Find P(#7)
odds: the ratio of favorable outcomes to
the number of unfavorable outcomes
number of favorable outcomes
O(T ) 
number of unfavorable outcomes
Ex 5
What are the odds
of rolling a 4 on a
standard number
cube?
Ex 6
What are the odds of rolling a 4 on a standard
number cube?
Find the odds of rolling a number greater than two.
What are the odds of rolling not a 2 or 3?
Ex 7
• A card is selected at random from a
standard deck of 52 cards. What are the
odds against selecting a 2 or a 3?