CONTEXT Recent advances in neonatology have influenced the incidence and severity of ROP in a dichotomous fashion. AIMS To determine the incidence of ROP and to analyse its risk factors. SETTINGS AND DESIGN Prospective clinical case series. MATERIALS AND METHODS 282 preterm infants with birthweight < 1500 g and/or gestational age ≤ 32 weeks and also those with gestational age > 32 weeks, ...

Appropriate statistical analyses are an integral part of surgical research. The purpose of this work is to assist surgeons and clinicians with the interpretation of statistics by providing a general understanding of the basic concepts that lead to choosing an appropriate statistical test for common study designs. It is extremely important to understand the nature of the data before embarking on...

Social environment risk factors present in schools and communities have not been thoroughly investigated. This study cross-sectionally examined the social environments of schools and communities, and their influence on adolescent alcohol and drug use. Survey responses of eighth grade students (N = 2309), a random half of their parents (n = 943), community leaders (n = 118), school principals (n...

These notes descibe various simple models and methods for analysis of longitudinal data and show how the analyses can be carried out using SAS. The descriptions require some knowledge of analysis of variance, also with random eeects as in split-plot experiments, in particular. Knowledge of multivariate analysis is not required, and the plain multivariate analysis of variance , treating each ser...