Control for confounding is crucial in causal observational studies. However, the modelling of continuous confounders has not received much attention. This is probably because in causal research the ...

Each term in a model, called an effect, is a variable or combination of variables. Effects are specified with a special notation using variable names and operators. There are two kinds of variables: ...

This section discusses how to specify the linear model that you plan to fit with the design. The OPTEX procedure provides for the same general linear models as the GLM procedure, although it does not ...

What is the Friedman test? The Friedman test, also sometimes referred to as Friedman’s two-way analysis of variance by ranks, is a non-parametric statistical test used to investigate whether groups of ...