Regression diagnostics are methods for determining whether a regression
model that has been fit to data adequately represents the structure of
the data. For example, if the model assumes a linear (straight-line)
relationship between the response and an explanatory variable, is the
assumption of linearity warranted? Regression diagnostics not only
reveal deficiencies in a regression model that has been fit to data but
in many instances may suggest how the model can be improved. The
Second Edition of this bestselling volume by John Fox considers two
important classes of regression models: the normal linear regression
model (LM), in which the response variable is quantitative and assumed
to have a normal distribution conditional on the values of the
explanatory variables; and generalized linear models (GLMs) in which the
conditional distribution of the response variable is a member of an
exponential family. R code and data sets for examples within the text
can be found on an accompanying website at https: //tinyurl.com/RegDiag.