The aims of the study were to establish the prevalence of erosion in a cluster random sample of 14-year-olds in Birmingham, UK and to determine whether socioeconomic group influences the prevalence of ...

Consider a population in which the variable of interest tends to be at or near zero for many of the population units but a subgroup exhibits values distinctly different from zero. Such a population ...

Cluster randomized trials in health care may involve three instead of two levels, for instance, in trials where different interventions to improve quality of care are compared. In such trials, the ...