Probability Created by Michele Hinkle and Jeffrey Fries March 2005.
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Transcript of Probability Created by Michele Hinkle and Jeffrey Fries March 2005.
Probability
Created byMichele 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.
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
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.
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.
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
• 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
• 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
• 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
• 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
The Probability Continuum
0
impossible
1
certain
1/2
equally
likely
unlikely likely