C532 Dec 5 2011

C532 Dec 5 2011 - C532: ANOVA & Regression Modeling Dec...

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C532: ANOVA & Regression Modeling Dec 5, 2011 Y. Cao 1 Topics: Learn how to use residual plot to assess model assumptions for multiple linear regression models and detect potential outliers and influential observations by influential graphics. Datasets : bodyfa.sav In a multiple linear regression, to assess the normality of the outcome variable we may use normal probability plot ; to see if the variances are the same for each observation of the explanatory variable and for each treatment group then residual plots in SPSS can help. To find possible outliers and influential observations we could follow the suggestions in today’s lecture note, for example, the scatter plot of Cook’s D or DfBeta s , DfFit s. If the Cook’s D is very large, we can remodel the data by excluding the outliers and/or influential observations that has the large Cook’s D values, and compare the models. The influential observations can be decided (by DeBetas’ DeFits) with the statistic values that have been given in the lecture note. We will realize some of these in our examples.
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C532: ANOVA & Regression Modeling Dec 6, 2010 Y. Cao 2 Go to Analyze > Regression > Linear We choose to include 2 “best” candidates for the explanatory variables, and the outcome variable is still the % fat method 1, as we used in the processing of find the best models in the Dec 1 tutorial. Click on Save… to select some more variables to create and to be used for detecting outliers and influential observations.
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C532: ANOVA & Regression Modeling Dec 6, 2010 Y. Cao 3 We choose to include Cook’s D and Standardized DfBeta(s) and Standardized DiFit Hit Continue to return.
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C532: ANOVA & Regression Modeling Dec 6, 2010 Y. Cao 4 Click on Plots… to continue. We want the Normal probability plot (highlight it) and the residual plot for
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This note was uploaded on 01/03/2012 for the course C 532 taught by Professor Long during the Fall '11 term at Palmer Chiropractic.

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C532 Dec 5 2011 - C532: ANOVA & Regression Modeling Dec...

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