Cost efficiency in study planning and completion. How many cases? How many controls?
One of the most important goals of a scientific study is to demonstrate a difference between comparison groups if one exists. Central to this goal is determination of sample size: too few subjects may result in erroneous conclusions or inability to reasonably exclude chance as an explanation, and too many subjects wastes time, money, and other resources. Either situation may also unnecessarily subject patients to risk of less effective treatments. Most researchers determine sample size using formulas that assume equal-sized comparison groups. Although these will assure that the study's statistical goals are met, the study will usually be more expensive than if unequal-sized groups are used. This report presents planning guidelines that consider the cost of subjects in determining the number of subjects for each group to assure that the study's statistical goals are met at minimal cost. As the study progresses, if costs and other factors are encountered that differ from assumptions that went into planning the study, the same techniques can be used to re-evaluate the most cost-effective group size.
D002986:Clinical Trials as Topic; D003362:Cost-Benefit Analysis; D006801:Humans; D010934:Planning Techniques; D012107:Research Design; D012306:Risk; D012494:Sampling Studies; D013223:Statistics as Topic