Power and sample size computations for the simultaneous assessment of the consistency of treatment effects

Wed, 27 Apr 2016 00:00:00 +0000

In this study power and sample size calculations for the analysis of treatment-by-subgroup interactions are proposed. Therefore, the interaction effect is either defined via product-type interaction contrasts or as ratio of treatment differences. The latter formulation allows besides the detection of interactions also the assessment of the consistency/heterogeneity of the subgroup-specific treatment effect by the definition of an inconsistency margin.

You can find the pdf of a detailed article here. Furthermore, the slides from a corresponding talk are given here.

Alternative effect size measurements corresponding to the two sample t-test

Fri, 05 Dec 2014 00:00:00 +0000

If interest is in comparing the means of two (normally distributed) samples it is common practise to perform a two-sample t-test and report the corresponding p-value. Nevertheless, it has been widely criticized that the p-value does not provide a measure for the magnitude of the mean effect (e.g., Browne (2010)). This report provides an overview of existing alternatives recently published in the scientific literature that provide a more meaningful measurement of the effect size. Browne (2010) introduced closed form equations to translate a significant t-test p-value and sample size into the probability of one treatment being more successful than another on a per individual basis. This term was afterwards denoted as win probability by Hayter (2013) and he demonstrated the interpretation as “what would happen if a single future observation were to be taken from either of the two treatments, with attention being directed towards which treatment would win by providing the better value.” In addition Hayter (2013) introduced the corresponding confidence interval as well as the odds of X being greater than Y. He further introduced the transformation into Cohens effect size and the corresponding confidence intervals.

You can find the pdf of a detailed article here

Projects | AKitsche Blog

Power and sample size computations for the simultaneous assessment of the consistency of treatment effects

Alternative effect size measurements corresponding to the two sample t-test