Date: 4/30/96 at 21:42:22 From: Gary L Knox Subject: Probability We got into quite a disagreement and would like another qualified opinion. It relates to the definition of probability. Our text says the probability of an event is a number between 0 and 1. One person thinks probabilities can be written only as a number from 0 to 1 like .732, etc. Another person says probabilities may be written as percents. Our question... is a probability number equal to a percent? Is it correct to say the probability is 42 percent, the way they do on the weather, or are they using sloppy wording? Gary
Date: 5/1/96 at 15:47:48 From: Doctor Ethan Subject: Re: Probability In my opinion, percents are a perfectly valid way to represent a probability. In essence both probabilities and percents measure ratios of occurrences, and so they both seem like very natural ways to represent the same concepts. In my experience, decimals are the most computationally efficient way to represent probabilities but I can think of cases where I would rather use fractions or percents. I think that the biggest problem (and maybe this is big enough) is linguistic awkwardness. Percents are usually used in a sentence like this: She got 93% of the answer right. (This is not a probability measure.) However, I think that we also might say She has a 93% chance of getting the next problem right. (This is a probability measure.) So I guess I would say that although there may be a pedagogical reason to keep the notation distinct, these are in fact both ways of expressing ratios of values, and therefore could be used interchangeably with consistency. -Doctor Ethan, The Math Forum Check out our web site! http://mathforum.org/dr.math/
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