Lesson 7.8

Simple Probability

Essential Question: How do you find the probability of an event?

Before we start…

You have a bag of M&M’s that contains: 6 red, 3 orange, 7 yellow, 5 green, 8 blue and 3 brown.

What is the fraction of red M&M’s to total M&M’s?

What is an outcome?

A possible result of an experiment.

Toss a coin: heads or tails.

Pick an M& M: red, orange, yellow, green, blue and brown.

What is an event?

Rolling an odd number on a dice.

Selecting a primary color M&M.

An outcome or a collection of outcomes.

What is a favorable outcome?

What you want to happen

The outcomes for a specific event

What is the probability of an event?

A measure of the likelihood or chance, that the event will occur, ranging from 0 to 1. Decimal, fraction or

percent

What are the types of probability?

• There are two types of probability– Theoretical probability– Experimental probability

What is theoretical probability?

When all outcomes of an event are equally likely.

The probability of event A is written as P (A)

How do you find theoretical probability?

Number of favorable outcomesTheoretical Probability = Total number of outcomes

Use the formula:

You and your friends designed T-shirts with silk screened emblems, and you are selling the T-shirts to raise money. The table below shows the number of T-shirts you have in each design. A student chooses a T-shirt at random. What is the probability that the student chooses a red T-shirt?

You toss a coin and roll a number cube. What is the probability that the coin shows tails and the number cube shows 4?

What is the probability that the spinner stops on an odd number?

What is the probability that the spinner stops on an even number?

What is the probability that the spinner stops on a multiple of 3?

Coin Toss Predict the number of times a coin will land heads up in 50 coin tosses.

What is experimental probability?

Based on the repeated trials of an experiment. Trials are how many

times experiment is performed

Successes are favorable outcomes

How do you find experimental probability?

Number of successesExperimental Probability = Number of trials

Use the formula:

Each section of the spinner shown has the same area. The spinner was spun 20 times. The table shows the results. For which color is the experimental probability of stopping on the color the same as the theoretical probability?

You spin the spinner 30 times. It stops on a multiple of 3 five times. What is the experimental probability of stopping on a multiple of 3?

Quality Control A company manufactures buttons. A quality control inspector finds 2 defective buttons in a batch of 300 buttons. About how many buttons would you expect to be defective in a shipment of 20,000 buttons?

How do you find the probability of an event?

Ticket Out the DoorYou roll a six sided number cube. What is the probability of rolling an even number?