# Parameterization of measurement error in brms

Thank you for putting the brms package together. I am using it for doing some analysis with measurement error in covariates. Do you have the exact parameterization of the measurement error model? From looking at the stan code, it looks like

x_{observed} \sim \text{Normal}(x_{true}, \sigma_{observed})

from this line in the stan code produced by brm()

target += normal_lpdf(Xn_1 | Xme_1, noise_1);

is that right?

Here’s a reproducible example

library(brms)

b0<-5; b1=2

x<- rnorm(30, mean = 20, sd=5)

xerr<-abs(rnorm(30, x*-.05, 2))

y<-rpois(30, b0+b1*x)

dat<-data.frame(y, x, xerr)

test<-brm(y~me(x, xerr) , dat, family = "poisson")


Thank you for all your help,

Corey Sparks
I don’t see xerr in your code though. and why did you truncate x?