ch. 8_101210 - Lab 227 10/12/10 Chapter 8 - Hypothesis...

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Lab 227 10/12/10 Chapter 8 - Hypothesis Testing and the Z-test What is hypothesis testing? A hypothesis test is a statistical method that uses sample data to evaluate a hypothesis about a population. o We evaluate whether our sample mean is different from our population mean. o In hypothesis testing, we can either reject or fail to reject the null hypothesis. o We want to find out if the difference between our sample mean and the population mean is likely to occur by chance. o The null hypothesis states that the difference has likely occurred by chance. o The research or alternative hypothesis states that the difference is unlikely to have occurred by chance. We define a critical region in our null distribution (usually 5%). If the sample mean falls in that region, it is unlikely that it belongs to the null distribution and therefore must belong to the alternative distribution. To compare our sample mean to the population mean, we use the sampling distribution of the mean. We compare the Z score of our sample mean, to the Z score marking the critical region. Example 1
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ch. 8_101210 - Lab 227 10/12/10 Chapter 8 - Hypothesis...

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