ch. 8_100709 - Lab 227 10/07/09 Chapter 8 - Hypothesis...

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Lab 227 10/07/09 Chapter 8 - Hypothesis Testing 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 alternate 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 means that has known properties. We don’t know how the population distribution looks like. We compare the Z score of our sample mean, to the Z score marking the critical region. Example 1 We are doing an experiment to see if a certain teaching method will help students get better math scores. Here are the results: μ = 85 M = 88 σ = 6.2 N = 30 We want to find out whether the sample mean is significantly different from the population mean. Step 1
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ch. 8_100709 - Lab 227 10/07/09 Chapter 8 - Hypothesis...

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