Probability is the measure of how likely an event is (written as a ratio)

Probability

is the measure of how likely an

event is (written as a ratio)

Probability of an Probability of an eventevent

The number of ways the event can occur divided by the total number of possible outcomes

P(A) = The number of ways an event can occur

Total number of possible outcomes

P(odd) =

Example#1: You roll a six-sided die whose sides are numbered from 1 through 6. a) What is the probability of rolling an ODD number?

36

.5

P(“t”) =

b) What is the probability of rolling a number that starts with the letter “t”?

26

.33

Example #2: A jar contains 6 red, 5 green, 8 blue and 3 yellow marbles.

P(red) =

P(green) = P(blue) = P(yellow) =

622

522

822

322

.27

.23 .36 .14

Example#2: A jar contains 6 red, 5 green, 8 blue and 3 yellow marbles.

P(orange) = 0 0

Example #3: A deck of cards contains 52 cards made up of 4 different suits – Hearts, Diamonds, Spades, and Clubs.

a) What is the probability of drawing a heart?

13

P Heart52

.25

b) What is the probability of drawing a 3?

c) What is the probability of drawing a face card?

4

P a 352

.08

12

P face52

.23

Practice #4 The table gives the handedness and eyedness of a randomly selected group of 100 people.

Right-Right-EyedEyed

Left-Left-EyedEyed

Right-Right-HandedHanded

57 31

Left-Left-HandedHanded

6 6

a) What is the probability of getting a left-handed person?

12100

.12


Left-Left-EyedEyed


57 31


6 6b) What is the probability of getting

someone who is left-eyed?37

100


.37

c) What is the probability of getting someone who is left-handed and is also left-eyed?


Left-Left-EyedEyed


57 31


6 6

6100


.06

d) What is the probability of getting someone who is right-handed and is also right-eyed?


Left-Left-EyedEyed


57 31


6 6

57100


.57

Practice #5The chart shows favorite subjects of students based on their gender.

MathMath SciencSciencee

EnglisEnglishh

SSSS

MaleMale 46 42 13 25FemalFemalee

12 21 45 36

a) What is the probability that a randomly chosen student likes Social Studies the most?

61240

.25


EnglisEnglishh

SSSS


12 21 45 36

b) What is the probability that a randomly chosen student is female?


.475114240


EnglisEnglishh

SSSS


12 21 45 36c) What is the probability that a

randomly chosen student both likes science and is a male?


.17542240


EnglisEnglishh

SSSS


12 21 45 36d) What is the probability that a

randomly chosen student likes social studies and is a female?


.1536240

Classwork!

Probability TablesProbability Tables

A Little Vocabulary Athletics

Music/Arts

SGA Other Total

Male Male total

Female Female

total

Total Athletics

totalMusic/arts

totalSGA total

Other total

Table total

Joint Probability

individual celltable total

Marginal Probability

column or row totaltable total

Conditional Probability

individual cellspecified row or column

Example 1•Using the table below, what is

the joint probability of a female that is involved in SGA?

Athletics Music/Arts

SGA Other Total

Male 10 5 1 2 18

Female 5 6 0 1 12

Total 15 11 1 3 30

0/30 = 0%


the marginal probability of choosing someone who is involved with athletics?


SGA Other Total

Male 10 5 1 2 18

Female 5 6 0 1 12

Total 15 11 1 3 30

15/30 = 50%


the conditional probability given that a person is male, that they are involved in Music/Arts?


SGA Other Total

Male 10 5 1 2 18

Female 5 6 0 1 12

Total 15 11 1 3 30

5/18 = 28%

CLASSWORKCLASSWORK

Task Handout

CLASSWORK/HOMEWORKCLASSWORK/HOMEWORK

Back of Task/Handout

Probability is the measure of how likely an event is (written as a ratio)

Documents

number of ways

favorite subjects of

selected group

odd number

yellow marbles

social studies

deck of cards

lefthanded person