Probability Created by Michele Hinkle and Jeffrey Fries March 2005.

11
Probability Created by Michele Hinkle and Jeffrey Fries March 2005

Transcript of Probability Created by Michele Hinkle and Jeffrey Fries March 2005.

Page 1: Probability Created by Michele Hinkle and Jeffrey Fries March 2005.

Probability

Created byMichele Hinkle and Jeffrey Fries

March 2005

Page 2: Probability Created by Michele Hinkle and Jeffrey Fries March 2005.

DefinitionsEvent:• Something that may

or may not happen.Probability:• The chance of an

event happening.Impossible:• An event that can

never happen.Certain:• An event that must

happen.

Page 3: Probability Created by Michele Hinkle and Jeffrey Fries March 2005.

The Probability Continuum

0

impossible

1

certain

1/2

equally

likely

If an event has a probability of ½, some

people say that there is a 50-50 chance that the

event will happen.

unlikely likely

Page 4: Probability Created by Michele Hinkle and Jeffrey Fries March 2005.

Making Predictions: Suppose you flip a

coin 20 times. How many times will it land heads up?

When you know the probability of an event, you can use this probability to make a prediction.

Page 5: Probability Created by Michele Hinkle and Jeffrey Fries March 2005.

Since the probability of a coin landing heads up is 1/2, you can predict that if you flip a coin 20 times, it will probably land heads up ½ of 20, or 10 times.

There is no guarantee that this will actually happen, but it is a reasonable prediction.

Page 6: Probability Created by Michele Hinkle and Jeffrey Fries March 2005.

Example: Describe the likelihood of picking a green egg from the bag.

• Since all the eggs are green, any egg you choose will be green. You are certain to pick a green egg.

4Number of favorable outcomes

Number of possible outcomes

4

Page 7: Probability Created by Michele Hinkle and Jeffrey Fries March 2005.

• Since no eggs are green, whichever egg you choose will not be green. It is impossible to pick a green egg.

Number of favorable outcomes

0

Number of possible outcomes

4

Page 8: Probability Created by Michele Hinkle and Jeffrey Fries March 2005.

• 2 of the 4 eggs, or ½ of the eggs are green. You have an equally likely chance of picking a green egg as not picking a green egg.

Number of favorable outcomes

2

Number of possible outcomes

4

Page 9: Probability Created by Michele Hinkle and Jeffrey Fries March 2005.

• It is unlikely, but not impossible, that you will pick a green egg from the bag that has only one green egg.

Number of favorable outcomes

1

Number of possible outcomes

4

Page 10: Probability Created by Michele Hinkle and Jeffrey Fries March 2005.

• It is likely, but not certain, that you will pick a green egg from the bag that has three green eggs.

Number of favorable outcomes

4

Number of possible outcomes

5

Page 11: Probability Created by Michele Hinkle and Jeffrey Fries March 2005.

The Probability Continuum

0

impossible

1

certain

1/2

equally

likely

unlikely likely