## the most patronizing start to an answer I have ever received

**A**nother occurrence [out of many!] of a question on X validated where the originator (*primitivus petitor*) was trying to get an explanation without the proper background. On either Bayesian statistics or simulation. The introductory sentence to the question was about “trying to understand how the choice of priors affects a Bayesian model estimated using MCMC” but the bulk of the question was in fact failing to understand an R code for a random-walk Metropolis-Hastings algorithm for a simple regression model provided in a introductory blog by Florian Hartig. And even more precisely about confusing the R code ** dnorm(b, sd = 5, log = T)** in the prior with

**in the proposal…**

*rnorm(1,mean=b, sd = 5, log = T)*

“You should definitely invest some time in learning the bases of Bayesian statistics and MCMC methods from textbooks or on-line courses.” X

So I started my answer with the above warning. Which sums up my feelings about many of those X validated questions, namely that *primitivi petitores* lack the most basic background to consider such questions. Obviously, I should not have bothered with an answer, but it was late at night after a long day, a good meal at the pub in Kenilworth, and a broken toe still bothering me. So I got this reply from the *primitivus petitor* that it was a patronizing piece of advice and he prefers to learn from R code than from textbooks and on-line courses, having “looked through a number of textbooks”. Good luck with this endeavour then!

April 30, 2015 at 9:38 am

As someone who (usually) actively doesn’t do it, I can tell you that Bayes = MCMC is a prominent assumption from a large cross section of the community. Maybe, sometimes, Bayes = “sampling-based inference”.

May 6, 2015 at 1:32 am

Dan

I encountered Bayes = MCMC when I was asked to explain Bayesian analysis to epidemiology students in 2005!!!

That is why I did this

http://stats.stackexchange.com/questions/41794/bayesian-updating-for-a-discrete-rating-value/43048#43048

As Don Fraser once said to me – its not obvious how to make the obvious obvious.

Keith O’Rourke

p.s. giving up does not work that well either.

May 6, 2015 at 9:13 am

Thanks, Keith! Without giving up, I wish some X’ed questioners would first check books before asking a question…

April 30, 2015 at 7:45 am

Hope your toe gets better. I can see where this guy is coming from; it’s hard to find time to just read the relevant literature. One is always tempted to look for short-cuts (although it almost always ends badly).

April 30, 2015 at 2:58 am

May your toe heal and feel better soon, Professor Robert!

April 30, 2015 at 2:58 am

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