This post summarizes Dablander, F.⭑, van den Berg, D.⭑, Ly, A., Wagenmakers, E.-J. (2020). Default Bayes Factors for Testing the (In)equality of Several Population Variances. Preprint available on ArXiv:                                     https://arxiv.org/abs/2003.06278. Abstract “Testing the (in)equality of variances is an important problem in many…

In a recent blog post, Bayesian icon David Spiegelhalter proposes a new analysis of the results from the ANDROMEDA-SHOCK randomized clinical trial. This trial was published in JAMA under the informative title “Effect of a Resuscitation Strategy Targeting Peripheral Perfusion Status vs Serum Lactate Levels on 28-Day Mortality Among Patients With Septic Shock”. In JAMA, the authors summarize their findings…

The Misconception The relative belief ratio (e.g., Evans 2015, Horwich 1982/2016) equals the marginal likelihood. The Correction The relative belief ratio is proportional to the marginal likelihood. Dividing two marginal likelihoods (i.e., computing a Bayes factor) cancels the constant of proportionality, such that the Bayes factor equals the ratio of two complementary relative belief ratios (Evans 2015, p.109, proposition 4.3.1).…

Available on https://psyarxiv.com/4pf9j, this is a comment on a recent article in JAMA (Futier et al., 2020). The multicenter FLASH trial1 concluded that “Among patients at risk of postoperative kidney injury undergoing major abdominal surgery, use of HES [hydroxyethyl starch] for volume replacement therapy compared with 0.9% saline resulted in no significant difference in a composite outcome of death or…

The default Bayes factor hypothesis test compares the predictive performance of two rival models, the point-null hypothesis and the alternative hypothesis . In the case of the -test, a popular choice for the prior distribution is a Cauchy centered on zero with scale parameter 0.707 (for informed alternatives see Gronau et al., in press). One of the problems with such…

In September 2018, the American Food and Drug Administration (FDA) issued a draft version of the industry guidance on “Adaptive Designs for Clinical Trials of Drugs and Biologics”. In an earlier blog post we provided some comments from a Bayesian perspective that we also submitted as feedback to the FDA. Two months ago, the FDA released the final version of…

Despite dying at a young age, Frank Ramsey has had a profound impact on the field of probability and inference. In his book Making decisions, Dennis Lindley lionizes Ramsey to the point of hyperbole:         “The basic ideas discussed in this book were essentially discovered by Frank Ramsey, who worked in Cambridge in the 1920s. To my…

In the previous post I discussed the famous de Finettti (1974) preface, containing the iconic statement “PROBABILITY DOES NOT EXIST”. As mentioned in that post, many statisticians and philosophers of science believe that, together with Frank Ramsey, de Finetti was the first real subjectivist. Fellow subjectivist Dennis Lindley, for instance, always expressed a fawning admiration for de Finetti, calling him…