Probability What are your Chances?

OverviewProbability is the study of random events.The probability, or chance, that an event will happen can be

described by a number between 0 and 1:

• A probability of 0, or 0%, means the event has no chance of happening.

• A probability of 1/2 , or 50%, means the event is just as likely to happen as not to happen.

• A probability of 1, or 100%, means the event is certain to happen.

For instance, the probability of a coin landing heads up is ½, or 50%, This means you would expect a coin to land “heads up”

half of the time.

Overview

The language of probability includes:• Experiment – a systematic investigation where the answer is unknown

You can represent the probability of an event by marking it on a number line like this one

Impossible 0 = 0%

Certain 1 = 100%

50 – 50 Chance½ , .5, 50%

number of possible outcomesProbability =

number of favorable outcomes

Ways to write Probability

FractionsPercent

OrDecimal

Most Common Way: Fraction or Percent

1. What is the probability that the spinner will stop on part A?

2. What is the probability that the spinner will stop on

(a) An even number?(b) An odd number?

3. What fraction names the probability that the spinner will stop in the area marked A?

AB

C D

3 1

2

A

C B

Probability Questions

• Lawrence is the captain of his track team. The team is deciding on a color and all eight members wrote their choice down on equal size cards. If Lawrence picks one card at random, what is the probability that he will pick blue?

yellow

red

blue blue

blue

green black

black

Coin Toss

Record your data on the handout that looks like this.

Toss a coin 25 times. Total the number of heads and tails. What percent was heads? Tails?

Toss a coin another 25 times. Total the number of heads and tails for this trial.

Add both trials together.

Is there a difference in the percentage when you calculate 50 tosses versus 25 tosses?

Squares in a Bag

1. Before doing the experiment. First, calculate the probability of choosing each color on your handout.

2. Then without looking, pick a square out of the cup 25 times.3. Record your scores.4. Calculate the experimental probability. 5. Compare the two amounts

There are 5 yellow, 3 blue, and 2 red squares in the cup.

Activity

Part 1Using 1 die with the numbers 1-6. Conduct a trial by rolling the die 100 times (25 each).

What do you think is the probability of picking a 1.

How many times did you roll 1, 2, 3, 4, 5, 6?

What is the percentage for each number?

Part 2Combine your 100 rolls with the 3 other people.

What is the percentage for each number out of the now 400 rolls/picks?