Statistical Sciences 2035 Quiz: Check residual statistics for outliers or influential cases
16 Oct 2018
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Check residual statistics for outliers or influential cases. Additionally, to the table seen above you can also check a histogram showing the frequency of the regression standardized residuals (as said on page (39) if this plot is roughly normal, you fulfilled the normality assumption) All values that tell us how extreme the prediction errors (residuals) are. Not very informative because the values are scale-dependent. Standardized & studentized residuals, leverage, cook"s distance explained. Much more informative because those are residuals expressed in z-scores. Somewhat tidier variant of the standardized residuals our preference. Studentized values smaller than -3 or larger than +3 = extreme prediction errors. If there is only 1 predictor in the regression model (as is the case here), such extreme values point to outliers in the y-direction of the scatterplot (i. e. vertical) Gives info of the existence of outliers in the x-direction of the scatter plot (horizontal: basically: unusual combination on scores of both predictors.
