Unit 6 Lesson 1 Understanding Probability

Essential Question: What is the likeliness of an event occurring based on the probability

near 0, 1/2, or 1?

Understanding Probability

• Probability is a number from 0 to 1 that shows the likelihood that an event will occur.–Probability close to 0 means an event is unlikely.• Example: Kevin Durant walking into our math class.

–Probability close to 1 means an event is likely.• Example: Our entire team being promoted to the 8th grade.

–Probability close to ½ means an event is neither likely or unlikely. There is an equal chance of the event occurring. • Example: A coin landing heads up.

Example 1

Describe each outcome using terms such as impossible, certain, likely, or equally likely.

Julia has a bag with 15 colored marbles in it.

A. The probability that Julia will draw a red marble from the bag is 1/15.

B. The probability that she will draw a green marble is 7/15.

Theoretical Probability

• Theoretical probability allows us to predict how many times an event would likely occur in a certain number of trials.

Experimental Probability

Since we do not live in a perfect world, your prediction may be close to, but not exactly equal to, your results. The actual outcomes are the experimental probability.

Example 2

A CD has only 1 pop song and 12 country songs on it. What is the probability that a song randomly selected at random will be a pop song? Determine if the event is likely, unlikely, or neither.

Are YOU Paying

Attention?

Suppose you roll a number cube with faces numbered 1 to 6. What is the probability of the cube landing on a number less than 7?

Guided Practice

• This spinner is divided into six congruent sections. What is the experimental probability of spinning a 2?1. Spin the spinner 18

times.2. Tally each time a

number is spun.3. Total the tally marks.

• My experimental probability of spinning a 2 was __________.

Number

Tallies

Times Spun

123456

Guided Practice

• Compare the your experimental probability to the theoretical probability of spinning a 2. Experimental probability: _____ Theoretical probability: _____

• The experimental probability that I found is _______________ the theoretical probability.

So, what do you remember?

Determine whether each event is impossible, unlikely, as likely as not ( same as equally likely), likely, or certain.

1. Bonnie’s Spanish club meets on Tuesday afternoons. How likely is it that Bonnie is at the mall on Tuesday afternoon?

2. There are 12 trucks and 12 cars in a parking lot. How likely is it that the next vehicle to move is a van?

Find the probability.3. It has rained on the last 2 out of 10 Fourth of July

parades in Swanton.a) What is the experimental probability that it will rain

this year?b) What is the probability that it will not rain this year?

Assignments

Classwork1. Textbook page 630 (1 – 5)2. Textbook page 634 (1 – 5)

Use one answer column for both pages.

Homework1. Introduction to Probability worksheet.

REMINDER: Classwork not completed in class should be completed as homework.

You can come in during homeroom to borrow a textbook to complete your classwork.

Or, you may take a picture, WITH PERMISSION, of the pages at the end of class.