2.8 - probability and odds
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Transcript 2.8 - probability and odds
Chapter 2 – Properties of
Real Numbers
2.8 – Probability and Odds
2.8 – Probability and Odds
Today we will be learning about:
Finding the probability of an event
Finding the odds of an event
2.8 – Probability and Odds
Probability of an event – measure of the
likelihood that the event will occur.
It is a number between 0 and 1
2.8 – Probability and Odds
Outcomes – different possible results
When an event has N equally likely outcomes,
each of them occur with probability 1/N.
Example: Rolling a six-sided number cube, the
possible outcomes are 1, 2, 3, 4, 5, and 6. The
probability associated with each outcome is 1/6.
2.8 – Probability and Odds
EVENT – all of the possible outcomes
THEORETICAL PROBABILITY - the
probability that should happen.
In the roll of a six-sided number cube, an “even
roll” consists of the outcomes 2, 4, and 6.
The theoretical probability of an even roll is 3/6 =
½.
FAVORABLE OUTCOMES – the outcomes
you wish to have happen.
2.8 – Probability and Odds
Theoretical Probability P =
Number of favorable outcomes
Total number of outcomes
2.8 – Probability and Odds
Another type of probability is
EXPERIMENTAL PROBABILITY. This
type of probability is based on repetitions of an
actual experiment and is calculated by the
following rule.
Experimental probability P =
Number of favorable outcomes observed
Total number of trials
2.8 – Probability and Odds
Example 1
You have 2 red and 2 black socks in a drawer.
You reach in and pick two without looking. What
is the probability P that they do not match
In a group of students, 12 ride the bus to school, 8
are driven to school, and 5 walk. One of the
students is chosen at random from the group.
What is the probability P that the student walks to
school?
2.8 – Probability and Odds
Example 2
Use the circle graph below showing the responses of 250
college students to a survey asking “Which factor is most
likely to influence your job choice after graduation?” If
you were to ask a randomly chosen college student this
question, what is the experimental probability that the
student would say “type of company?”
Salary93
location103
Type of
company
37
Size of
company
17
2.8 – Probability and Odds
THE ODDS OF AN EVENT
When all outcomes are equally likely, the ODDS
that an event will occur are given by the formula:
ODDS = Number of favorable outcomes
Number of unfavorable outcomes
2.8 – Probability and Odds
Example 3
You randomly choose a letter from the word
SUMMER. What are the odds that the letter is a
vowel?
2.8 – Probability and Odds
Example 4
The probability that a randomly chosen 4 digit
security code contains at least one zero is 0.34.
What are the odds that a 4 digit security code
contains at least one zero?
2.8 – Probability and Odds
HOMEWORK
Page 117
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