title: Testing for qualitative interaction using ratios of treatment differences.
abstract: Testing for or against a qualitative interaction is relevant in randomized clinical trials that use a common primary factor treatment and have a secondary factor, such as the centre, region, subgroup, gender or biomarker. Interaction contrasts are formulated for ratios of differences between the levels of the primary treatment factor. Simultaneous confidence intervals allow for interpreting the magnitude and the relevance of the qualitative interaction. The proposed method is demonstrated by means of a multi-centre clinical trial, using the R package mratios.
authors.affiliation: Institut für Biostatistik, Leibniz Universität Hannover, Herrenhäuser Straße 2, 30419 Hannover, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Kitsche
authors.forename: Ludwig A
authors.initials: LA
authors.lastname: Hothorn
mesh_terms: D016001:Confidence Intervals; D003627:Data Interpretation, Statistical; D015337:Multicenter Studies as Topic; D017063:Outcome Assessment, Health Care / Q000706:statistics & numerical data*; D016032:Randomized Controlled Trials as Topic / Q000706:statistics & numerical data*; D013223:Statistics as Topic / Q000379:methods*
keywords: consistency; heterogeneity; qualitative interactions; ratios of differences; simultaneous confidence intervals