Odds |
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We often want to know the odds in favor or the odds against a certain event, such as the president being re-elected. If the odds of the president being re-elected are four to one, we write the odds as a proportion 4:1. The president will be re-elected four times for every one time he is not re-elected. Odds notation compares a given event to its complement (the opposite event). This translates into probability by choosing the left number as the numerator and the sum of the two numbers as the denominator. The probability of re-election is 4/5 = .8 = 80% |
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EXAMPLE |
When you roll a die, the outcomes
are equally likely. The odds for rolling a six on a die are 1:5. The
odds against rolling a six on a die are 5:1. The odds of rolling a
number greater than four are 2:4. The odds against rolling an odd
number are 3:3, which are even odds.
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Gambling against the oddsCasinos have an advantage where the
house always wins a portion of the money you gamble. If you're betting
$100 an hour on roulette, you will lose, on average, $5.26 an hour,
which goes to the house. The odds on slot machines are the worst --
casinos make two-thirds of their profit on slots.
In horse racing, the house typically keeps 17% of all money bet. Besides that, they "round down" to the nearest dime, so you lose about 2% more. The odds of winning the California Super Lotto Jackpot are 1:18 million. You would have to buy 50 Lotto tickets each week in order to win the jackpot once in every 5000 years! It is three times more likely for you to be killed driving ten miles to the store to buy a lotto ticket than to win the jackpot. Compare the lotto odds to some of the following odds for dying: |
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