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2016 ; 4
(10
): 195
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Residuals and regression diagnostics: focusing on logistic regression
#MMPMID27294091
Zhang Z
Ann Transl Med
2016[May]; 4
(10
): 195
PMID27294091
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Up to now I have introduced most steps in regression model building and
validation. The last step is to check whether there are observations that have
significant impact on model coefficient and specification. The article firstly
describes plotting Pearson residual against predictors. Such plots are helpful in
identifying non-linearity and provide hints on how to transform predictors. Next,
I focus on observations of outlier, leverage and influence that may have
significant impact on model building. Outlier is such an observation that its
response value is unusual conditional on covariate pattern. Leverage is an
observation with covariate pattern that is far away from the regressor space.
Influence is the product of outlier and leverage. That is, when influential
observation is dropped from the model, there will be a significant shift of the
coefficient. Summary statistics for outlier, leverage and influence are
studentized residuals, hat values and Cook's distance. They can be easily
visualized with graphs and formally tested using the car package.