“If you give a man a fish he is hungry again in an hour. If you teach him to catch a fish you do him a good turn. But, if instead you convince him that catching fish is far too complicated a business for a neophyte like himself and he’d be better off forgetting all about fish catching and just damn well pay you to do it for him, then you have done yourself a good turn.” — Anne “Astrostatistics” Thackeray
This famous quotation sprang to mind upon (re-)reading Ned Taylor’s paper on Bayesian modelling of the red/blue galaxy bimodality on astro ph today. Although I’d seen a near-identical early draft of this manuscript a couple of years ago I was stuck (again) by the sheer degree of obfuscation in the presentation of a truly simple hierarchical modelling problem: a generative model that could be written in a paragraph of hierarchical notation, directly transcribable into JAGS or STAN, is instead built up piece-by-unnecessariy-confusing-and-slightly-“patrician”-piece in a six page appendix plus great discussions in the main body (btw. these are two column small font pages). My impression is that a lot of astro-statisticians are working this angle to carve out a niche for themselves and create demand where it barely existed before; unflattering comparisons to nutritionists and life coaches spring to mind.
Having said that, I haven’t had the time to thoroughly check out the proposed model and fitting procedure, but I’d be surprised if there was anything wrong with them; and the idea of using a Bayesian mixture model to quantify the red and blue sequence is an entirely sensible one.
(The only thing that caught my eye on first inspection was the very wooly statement that asymptotically AIC ~ BIC ~ DIC ~ -2 log-Bayes factor. Sure, if you consider an order(1) approximation.)