Unformatted text preview: M316 Chapter 10 Dr. Berg Introducing Probability Probability is a measure of likelihood and likelihood plays a critical role in statistics. Example (10.1) Do You Lotto? What proportion of all adults bought a lottery ticket in the past 12 months? We don't know, but we do have results from the Gallup Poll. Gallup took a random sample of 1523 adults. The poll found that 868 of the people in the sample bought tickets. The proportion who bought tickets was 868 sample proportion = = 0.57 or about 57%. 1523 Because all adults had the same chance to be among the 1523, it seems reasonable to use 57% as an estimate for the true proportion of the population that bought lottery tickets. Could it happen that one random sample finds that 57% bought lottery tickets and a second random sample finds that 37% bought lottery tickets? Random samples eliminate bias from the act of choosing a sample, but they can still be wrong because of the variability that results when we choose at random. Because Gallup uses chance to choose i...
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- Fall '08
- Probability, Probability theory, Dr. Berg