Published online by Cambridge University Press: 21 June 2016
Clinical epidemiologic studies often focus on the identification of risk factors associated with hospital-acquired infections and the subsequent effects of preventive measures. Two study designs commonly used are the prospective design and the retrospective design. Both of these designs and the associated data collection issues were defined and discussed in the first article of this series. This article reviews the statistical analysis for a dichotomous risk factor and the presence or absence of a given disease for unmatched data. We focus our attention primarily on the unmatched prospective study, although we present formulae for the retrospective study as well.