Although randomized controlled trials provide the highest level of evidence for causation,
many clinical issues cannot be addressed using experimental study design. Examples that …

The proper interpretation of research findings in obstetrics and gynecology increasingly
requires some understanding of epidemiology and biostatistics. The disciplines of …

Prospective and retrospective cohorts and case-control studies are some of the most
important study designs in epidemiology because, under certain assumptions, they can …

Case-control studies begin at the end. Two groups of patients, those with disease (cases)
and those without (controls), are compared to determine the degree of exposure to a …

A comparative controlled trial is designed to assess the relative effectiveness of two or more
treatments (exposures). Because investigators strive to identify the better treatment if one …

Observational studies, when done well, enable inferences of causal associations. However,
most observational studies cannot achieve inferences regarding causality, because of the …

The study of causal relationships is important when addressing questions of efficacy of
treatment interventions and etiology of disease. The evaluation of a cause-and-effect …

Learning points Case–control studies are an efficient method for the study of rare outcomes,
but suffer various limitations, including susceptibility to bias in recollection about exposure; …

The cross-sectional study design is sometimes avoided by researchers or considered an
undesired methodology. Possible reasons include incomplete understanding of the …

The goal of epidemiology is accurate measure of the relationship between an exposure and
a disease of interest. The control of covariates of the exposure-disease relationship is …