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A method is developed to calculate the required number of subjects k in a reliability study, where reliability is measured using the intraclass correlation rho. The method is based on a functional approximation to earlier exact results. The approximation is shown to have excellent agreement with the exact results and one can use it easily without intensive(More)
OBJECTIVE Results of reliability and agreement studies are intended to provide information about the amount of error inherent in any diagnosis, score, or measurement. The level of reliability and agreement among users of scales, instruments, or classifications is widely unknown. Therefore, there is a need for rigorously conducted interrater and intrarater(More)
BACKGROUND We designed this observational cohort study to assess the association between patient-centered communication in primary care visits and subsequent health and medical care utilization. METHODS We selected 39 family physicians at random, and 315 of their patients participated. Office visits were audiotaped and scored for patient-centered(More)
This paper provides exact power contours to guide the planning of reliability studies, where the parameter of interest is the coefficient of intraclass correlation rho derived from a one-way analysis of variance model. The contours display the required numbers of subjects k and number of repeated measurements n that provide 80 per cent power for testing Ho:(More)
BACKGROUND We undertook a multicentre randomised controlled trial that compared the standard model of antenatal care with a new model that emphasises actions known to be effective in improving maternal or neonatal outcomes and has fewer clinic visits. METHODS Clinics in Argentina, Cuba, Saudi Arabia, and Thailand were randomly allocated to provide either(More)
OBJECTIVE To assess the risks and benefits associated with caesarean delivery compared with vaginal delivery. DESIGN Prospective cohort study within the 2005 WHO global survey on maternal and perinatal health. SETTING 410 health facilities in 24 areas in eight randomly selected Latin American countries; 123 were randomly selected and 120 participated(More)
It is now well known that standard statistical procedures become invalidated when applied to cluster randomized trials in which the unit of inference is the individual. A resulting consequence is that researchers conducting such trials are faced with a multitude of design choices, including selection of the primary unit of inference, the degree to which(More)
BACKGROUND Caesarean delivery rates continue to increase worldwide. Our aim was to assess the association between caesarean delivery and pregnancy outcome at the institutional level, adjusting for the pregnant population and institutional characteristics. METHODS For the 2005 WHO global survey on maternal and perinatal health, we assessed a multistage(More)
OBJECTIVE To determine whether an interactive curriculum that integrates dating violence prevention with lessons on healthy relationships, sexual health, and substance use reduces physical dating violence (PDV). DESIGN Cluster randomized trial with 2.5-year follow-up; prespecified subgroup analyses by sex. SETTING Grade 9 health classes. PARTICIPANTS(More)