HOMEWORK QUESTIONS?

5.2TW

O-WAY

TABLE

S

PROBABILITY MODELS

A probability model describes chance behavior by listing the possible outcomes in the sample space and giving the probability that each outcome occurs.

Example:Color of Marble

Red Green Blue

Probability 0.4 0.1 0.5

BASIC RULES OF PROBABILITY

ARE THESE MUTUALLY EXCLUSIVE?

• Turning left and turning right

• Drawing a king and drawing an ace

• Tossing a coin

• Drawing a king and drawing an ace

• Turning your head and scratching your foot

ADDITION RULE FOR MUTUALLY EXCLUSIVEIf A and B are mutually exclusive, P(A or

B) = P(A) + P(B)

For example, find the probability that you pull an ace or a king out of a deck of cards.

ANOTHER EXAMPLE

In a game of soccer, the probability of scoring no goals (event A) is 20%. The probability of scoring exactly 1 goal (event B) is 15%.

Find P(A and B)

Find P(A or B)

TWO-WAY TABLES

Students in a college statistics class wanted to find out how common it is for young adults to have their ears pierced. They recorded data on two variables – gender and whether the student had a pierced ear – for all 178 people in the class. Here is the two-way table describing their results.

Suppose we choose a student at random. Find the probability that the student:

a) has pierced ears

b) is a male with pierced ears

c) is a male or has pierced ears

Gender Yes No Total

Male 19 71 90

Female 84 4 88

Total 103 75 178

Define events!

A – is male

B – has pierced

ears

ONE MORE EXAMPLE

Let A be the event that the person is a female and B be the event that the person is underweight. Try to answer these on your own:

1.P(A) =

2.P(B) =

3.P(A or B) =

4.P(A and B) =

HOMEWORK

Pg 308 (39-50)Check Mr. Suk’s website for extra help videos! They will really help you along the way!