1. Application of Probability
Probability involves the likelihood of events occurring.
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2. Using a percent:
How would you describe the chances that something is
guaranteed to happen?
How would you describe tne chances that something is
guarenteed to not happen?
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3. The probability of an individual event occurring can be
represented on a probability scale as follows.
* an impossible event has a probability value of 0
* a certain event has a probability value of 1
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4. Example 1
Place the following events on a probability scale.
1. The sun will rise in the east next Sunday.
2. The next baby born in your local hospital will be a boy.
3. Somewhere in Manitoba, the temperature will reach at least 4° C
once next year during the month of January.
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5. A convenient way of expressing the probability of an event occurring
is to use the notation: P(event)
For example,
The probability of flipping a coin and having it land heads can be
expressed as: P(H) = 1 : 2
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6. An event has to either occur or not occur, the probability of an event
occurring plus the probability of an event not occurring is a certainty
and equal to 1.
This relationship can be expressed as:
P(event occurring) + P(event not occurring) = 1
P(event not occurring) = 1 ­ P(event occurring)
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7. Probability can be expressed in the following ways:
* a fraction
* a ratio
* a decimal
* a percent
* in words
* on a probability scale
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8. Example 2
Two coins are tossed.
1. Determine all possible outcomes.
2. Express the probability of both coins landing heads in the following
ways:
* a fraction
* a ratio
* a decimal
* a percent
* in words
* on a probability scale with a scale in decimals
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9. P(HH) = 1 : 4
* a fraction: 1/4
* a ratio: 1 : 4
* a decimal: 0.25
* a percent: 25%
* in words: The probability that the two coins will land heads is 1 out of 4.
* on a scale:
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10. Assignment
page 324
Questions 1 ­7
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