 Objective:
Probability
In this lesson you will demonstrate an understanding
of measures of chance, use counting procedures and
calculations to determine the number of outcomes and/or
probability of a simple event, and compare results
of experiments and simulations with mathematical probabilities.
If you need to check a word's definition, please go to the glossary by clicking the Vocabulary button
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probability
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outcome
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random
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combination
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permutation
Tips to Remember:
Probability of Any Outcome
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The probability of any outcome
is always a number from 0 to 1 and tells you how
likely something is to happen. For example, if
you have a probability of 1/4 it means that the
event you are looking for could be expected to
occur once every 4 times. If you have the probability
of 0 it means the event is impossible and doesn't
occur, while the probability of 1 means the event
will happen each time.
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Writing Probabilities
| Probabilities may be written as
a fraction, a decimal, or percent. For example, if
you have a probability of 1/5, it can be written as
1/5, .20, or 20%. All three are acceptable ways of
writing a probability. |
Fair Game
| A game is considered fair if each
player has the same chance of winning. |
Outcomes
| The result of a single trial of
an experiment is called an outcome. If each outcome
has the same chance of occurring, the outcomes are
equally likely. |
Determining a Probability
There are
three common ways used to determine probabilities.
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The first way is to basically guess.
For example, you want a car and you may tell your
friends that there is a 50% or 1/2 you will get a
new car. You are just guessing because there really
isn't any other way to calculate this probability.
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Another way includes actually
doing an experiment to see the number of outcomes
desired
and then choose the probability based upon your
results.
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Lastly, is to assume that all
outcomes are equally likely. For example, when
flipping a
coin it can either land on heads or tails. Because
there are two possible outcomes, heads or tails,
the probability of landing on either heads or
tails would be 1/2 or 50%.
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Probability Formulas for Equally Likely Outcomes
A situation has N equally
likely possible outcomes and an event includes E of
these. Let P be the probability that
the event will occur. Therefore:
P = E/N
If the probability that an event
will occur is P, then the probability
that the event will not occur is 1 - P. |
Example
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