Transcript Probability - Cloudfront.net

Representing Probability
Lesson 11-2
Pg. # 420-421
CA Content Standards
Statistics, Data Analysis, and Probability 3.3 ***:
I represent probabilities as ratios; I know that if P
is the probability of an event, 1- P is the
probability of an event not occurring.
Statistics, Data Analysis, and Probability 3.0:
I determine theoretical and experimental
probabilities and use these to make predictions
about events.
Review Vocabulary:
PROBABILITY
A measure of how likely it is that some
event will occur.
Ratio: Number of favorable outcomes
Number of all possible outcomes
Review Vocabulary:
CERTAIN EVENT
An event that is sure to happen.
Has a probability of 1.
For example:
Probability (green) = 5 = 1
5
Review Vocabulary:
IMPOSSIBLE EVENT
An event that cannot happen.
Has a probability of 0.
For example:
Probability (orange) = 0 = 0
5
Objective
Write probabilities as fractions, decimals, and
percents.
Math Link: You know how to write probabilities
as a ratio. Now you will learn how to represent
probabilities in other forms.
Example 1.
What is the probability that the spinner will
land on green?
P(green) = favorable outcomes
possible outcomes
P(green) = 4 green
8 total
P(green) = 4 = 1
8 2
Example 2.
What is the probability that the spinner will NOT land on
yellow?
First find the probability that the spinner will land on
yellow.
P(yellow) = favorable outcomes
possible outcomes
P(yellow) = 2 = 1
8 4
P(not yellow) = 1 - P(yellow)
= 1 - 1 /4
= 3/ 4
Here’s Why It Works
P(not yellow) means the spinner can land on any
color but yellow… including green, red, and blue.
There are 6 sections that are not yellow.
P(not yellow) = 6/8
Each outcome is either yellow or not yellow, so:
P(yellow) + P(not yellow) = 2/8 + 6/8 = 8/8 =1
Therefore, P(not yellow) = 1 - P(yellow)
Example 3.
What is the probability the spinner will land on green
or red.
Since five sections are either green or red…
P(green or red) = favorable outcomes
possible outcomes
P(green or red) = 5
8
CHALLENGE:
Find P(green AND red)
Moral of the Story
Probabilities can be written as fractions,
decimals, and percents.