Workshop14 - CHEN 3010 Applied Data Analysis Names: Fall...

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CHEN 3010 Applied Data Analysis Fall 2003 Names: __________________________ Workshop #14 Inferences on the Variance Background Hypothesis tests and confidence interval calculations involving the variance occur in a number of practical situations. For example, an important measure of a product is the variability in a particular quality measure. In manufacturing a polymer film, variability in film thickness must be kept at or below a specification, and quality can be improved by decreasing the variability, effectively narrowing the distribution of film thicknesses. When estimating the mean from sample averages, we were able to take advantage of the central limit theorem, whereby the distribution of sample averages, X , tends toward a normal distribution even though the distribution of the variable measured, X , can be quite different from normal. That is not the case when working with the variance. Here, the method outlined is based on the assumption that the variable measured, XN () μ σ , 2 , that is, X is described by
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Workshop14 - CHEN 3010 Applied Data Analysis Names: Fall...

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