# What is the difference between Intercept and b\_Intercept?

**URL:** <https://discourse.mc-stan.org/t/what-is-the-difference-between-intercept-and-b-intercept/20423>\
**Category:** Modeling\
**Tags:** brms\
**Created:** [January 25, 2021, 6:48pm UTC](https://discourse.mc-stan.org/t/what-is-the-difference-between-intercept-and-b-intercept/20423 "2021-01-25T18:48:24Z")\
**Posts on this page:** 1\
**Showing post:** 7

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**Author:** ![andrjohns](https://yyz2.discourse-cdn.com/flex030/user_avatar/discourse.mc-stan.org/andrjohns/32/15297_2.png) [@andrjohns](https://discourse.mc-stan.org/u/andrjohns)\
**Post date:** [January 26, 2021, 6:07am UTC](https://discourse.mc-stan.org/t/what-is-the-difference-between-intercept-and-b-intercept/20423/7 "2021-01-26T06:07:06Z")

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Hi Britta,

If you look at the underlying Stan code for the model using:

```
make_stancode(data = data,
    formula = x ~ y,
    seed = 1,
    save_pars = save_pars(all=TRUE))

```

You’ll see the respective definitions:

```
parameters {
  vector[Kc] b; // population-level effects
  real Intercept; // temporary intercept for centered predictors
  real<lower=0> sigma; // residual SD
}
...
generated quantities {
  // actual population-level intercept
  real b_Intercept = Intercept - dot_product(means_X, b);
}

```

This is referring to the fact that `brms` mean-centers the predictors prior to analysis, so the `Intercept` parameter is on the mean-centered scale. The `b_Intercept` parameter is this mean-centered intercept back-transformed to the original scale of the predictors

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_[View the full topic](https://discourse.mc-stan.org/t/what-is-the-difference-between-intercept-and-b-intercept/20423)._