background: tobacco smoking is the leading cause of preventable mortality. the prevalence of smoking in adolescents in high schools ranges from 23.5% to 41%, respectively. in colombia, these figures are similar and students entering the university are exposed to initiate smoking. the purpose of this study was to establish the determinants associated with the initiation of tobacco smoking among ...

This paper discusses the statistical principles, methods, and software programs used to calculate sample size. In addition, it reviews the practical challenges faced in calculating sample size. We show that because of such challenges, statistical calculations often do not provide us with a clear-cut number for the study sample size; rather they suggest a range of reasonable numbers. The paper a...

Methods Problems in the design of epidemiologic studies may be categorized conveniently into those related to ascertainment and those concerned with sampling. Sampling problems confronted in home accident studies are not different, in any essential way, from those encountered in any other epidemiologic studies. With reference to sampling, the epidemiologic critics are far in advance of epidemio...