title: [Roaming through methodology. XXXIII. Ethics of sample size estimation: less subjects needed for a one-sided than for a two-sided statistical investigation].
abstract: In sample size calculations for clinical trials, two-sided statistical testing is the usual starting point. Compared with one-sided testing, this option requires the inclusion of a larger number of study subjects, and a larger number of study events will be needed before a conclusion can be reached. It is therefore ethically relevant to consider in which situations one-sided testing should be the preferred option. One-sided statistical testing is preferable when the research hypothesis is one-sided (is intervention A better and intervention B?), or when only a clearly better result for A compared to B will have clinical consequences (e.g. if A is more cumbersome or more invasive to the patient than B). For the estimation of the number of study subjects needed, one-sided testing should then be assumed. If a new intervention is to be tested by comparison with placebo treatment or with absence of treatment, one-sided testing is an adequate starting point for sample size estimation.
authors: Universiteit Maastricht, Onderzoeksinstituut voor Extramurale en Transmurale Gzondheidszorg (ExTra), Postbus 616, 6200 MD Maastricht.
authors: J A
authors: JA
authors: Knottnerus
authors: L M
authors: LM
authors: Bouter
mesh_terms: D016022:Case-Control Studies; D002986:Clinical Trials as Topic / Q000379:methods* / Q000592:standards; D003627:Data Interpretation, Statistical; D004992:Ethics, Medical; D006801:Humans; D012107:Research Design / Q000592:standards*; D018401:Sample Size