Longitudinal data arise whenever repeated measurements are taken on the same experimental units over time or under varying conditions. Generalized estimating equations (GEE) provide a popular marginal ...

The TEACH Project obtained subjects' time-location information as part of its assessment of personal exposures to air toxics for high school students in two major urban areas. This report uses a ...

A categorical variable is defined as one that can assume only a limited number of values. For example, a person's sex is a categorical variable that can assume one of two values. Variables with levels ...