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Unformatted text preview: Introduction to Hypothesis Testing 9 of 14 Tells us the likelihood of supporting a true alternative hypothesis (making the correct decision). Good tests have powers of at least 0.80.9. Generally not simple to calculate, depends on (1) level, (2) sample size, (3) effect size, (4) specific test being used, (5) variance in population, ... Before doing a study to support a hypothesis: you should determine the minimum effect size you wish to detect and the desired power, then calculate the required n . If we fail to reject the null hypothesis there are 3 possibilities: 1. The null hypothesis is true, there is no true effect. (Must calculate to support this conclusion.) 2. The study design is too weak to detect a true alternative hypothesis (true effect). 3. The study had a good power, but random chance (sampling error) pre vented us from rejecting a true alternative hypothesis. Importance of Power Analysis: Before conducting a study, we need to ensure that the sample size is large enough so it will be likely that we can actually detect a true alternative hy pothesis. If the study design is too weak, the alternative hypothesis may be true but it is unlikely that we would be able to detect this. To determine the sample size n we must decide what is the minimum effect size difference from the null hypothesis that we are interested in detecting. 1.3 Single sample proportion test USE Often used to help answer: 1. Is the proportion of a population equal to p ? Is the proportion of people who smoke 20%? 2. Is the proportion of a population different than p ? Is the proportion of people who smoke more than 20%? Is the proportion of contaminants in the water below the EPA standard? COMPUTATION Single sample proportion test. Definition 1.8 To support an alternative hypothesis concerning a population propor tion: requirements (1) simple random sample, (2) binomial distribution, (3) normal approximation of binomial np, nq 5....
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This note was uploaded on 02/10/2012 for the course MAT 1670 taught by Professor Tanbakuchi during the Spring '11 term at University of Florida.
 Spring '11
 Tanbakuchi
 Statistics

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