Bayesian estimation in a new web app!

January 4, 2013

(This article was originally published at Doing Bayesian Data Analysis, and syndicated at StatsBlogs.)

A wonderful new web app is now available for doing Bayesian estimation of two groups. Just enter the data for each group, click the "go" button, and watch the MCMC sample emerge, revealing the posterior distribution for the means, standard deviations, and normality, along with the difference of means, difference of standard deviations, and effect size. This web app was created by Rasmus Bååth and is available at Give it a try!
The web app is fabulous for quickly and easily seeing the main results of a Bayesian estimation of parameters for two groups. There is no need to install R and JAGS and then invoke R and run commands. Instead, just paste in your data and click a button!

Here (below) is a screen shot from January 03, 2013, using the data from the main example of BEST. More comments about the app continue after the screen shot.

The original implementation of BEST, available from, provides some more functionality than in the app (at the time of this post), but only by taking the effort to install (free) software and to interact with the R programming language. The original BEST software implements ROPEs for the decision rule and shows a posterior predictive check in the form of a smattering of credible model distributions superimposed on data histograms. It also shows correlations of parameters in the posterior. The original BEST software also does power computations. Another benefit of dealing with the BEST software is that it is a gateway to the full spectrum of Bayesian data-analysis programs written in R and JAGS/BUGS. But for quickly and easily showing the primary results from a Bayesian analysis of two groups, this web app is brilliant!

Big thanks to Rasmus Bååth for creating this awesome web app! If you like it, let him know -- his e-mail is linked in the lower right "About" section on the web app. The URL again is

Please comment on the article here: Doing Bayesian Data Analysis