IntroStat-notes 12-05-07

# IntroStat-notes 12-05-07 - -left-tailed tests are for less...

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-the test statistic is a value used in making a decision about the null hypotheses, and is found by converting the sample statistic to a score with the assumption that the null hypothesis is true -the critical region/rejection region is the set of all values of the test statistic that cause us to reject the null hypothesis -the significance level (denoted by alpha) is the probability that the test statistic will fall in the critical region when the null hypothesis is actually true; common choices for alpha include .05, .01, and .1 -a critical value is the value that separates the critical region (where we reject the null hypothesis) from the values of the test statistic that do not lead to rejection of the null hypotheses. The critical values depend on the nature of the null hypothesis, the sampling distribution that applies, and the significance level (alpha) -two-tailed, right-tailed, and left-tailed tests -the tails in a distribution are the extreme regions based on critical values -right-tailed tests are for greater than
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Unformatted text preview: -left-tailed tests are for less than-two-tailed tests are for not equal to-the p-value/probability value is the probability of getting a value of the test statistic that is at least as extreme as the one representing the sample data, assuming that the null hypothesis is true. The null hypothesis is rejected if the p-value is very small, such as .05 or less-conclusions in hypothesis testing-we always test the null hypothesis. The initial conclusion will always be 1.) reject the null hypothesis, or 2.) fail to reject the null hypothesis-reject the null hypothesis if the test statistic falls within the critical region-fail to reject the null hypothesis if the test statistic does not fall within the critical region-p-value method: reject the null hypothesis if the p-value is less than or equal to alpha; fail to reject if the p-value > alpha-instead of using a significance level such as .05, you could simply identify the p-value and leave the decision to the reader...
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