Odds Slang for Probability?Date: 02/06/97 at 15:44:00 From: Anonymous Subject: Odds and probability What is the difference between odds and probability? Or is odds a slang term for probability? Date: 02/06/97 at 21:41:26 From: Doctor Wallace Subject: Re: Odds and probability No, odds is not slang for probability. There is a difference. A probability is a number from 0 to 1 inclusive, usually expressed as a fraction, which is the ratio of the number of chances of a specific event to the total number of chances possible. For example, if I have 4 marbles in a jar, 3 red and 1 blue, then the probability of drawing the blue is 1/4. There is one chance of a blue marble and 4 total chances (marbles). Odds are expressed as the number of chances for (or against) versus the number of chances against (or for). So, since there is 1 chance of your picking the blue, and 3 chances of your picking red, the odds are 3 to 1 AGAINST you picking the blue. For odds in favor, we just reverse them. The odds are 1 to 3 IN FAVOR OF you picking the blue. This can be a little confusing, so I'll say it again. If you express odds as AGAINST, you put the number of chances against first, versus the number of chances for. If you express odds as IN FAVOR OF, you put the chances for the event happening first. Note that this does NOT mean that the probability is 1/3 for or against in the above example. To convert odds to probability, we have to ADD the chances. So, if the odds against a horse winning are 4 to 1, this means that, out of 5 (4 + 1) chances, the horse has 1 chance of winning. So the PROBABILITY of the horse winning is 1/5 or 20 percent. I hope this helps. If you need more assistance, don't hesitate to write back! -Doctor Wallace, The Math Forum Check out our web site! http://mathforum.org/dr.math/ |
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