There is increasing interest in the medical world in the possibility of tailoring treatment to the individual patient. Statistically, the relevant task is to identify interactions between covariates and treatments, such that the patient’s value of a given covariate influences how strongly (or...

I provide a new tool (marginscontplot) for plotting the marginal effect of continuous covariates in regression models. The plots may be univariate or according to levels or user-selected values of a second covariate. Nonlinear relationships involving transformed covariates may be plotted on the...

Assessing the instability of a multivariable model is important but is rarely done in practice. Model instability occurs when selected predictors--and for multivariable fractional polynomial modeling, selected functions of continuous predictors--are sensitive to small changes in the data....