Exercise

# R-squared for a Bayesian Model

Now let's calculate the R-squared for a Bayesian model so we can assess the predictions of models estimated with `stan_glm`

. The `stan_model`

object is already loaded.

Instructions

**100 XP**

- Calculate the variance of the residuals of
`stan_model`

- Calculate the variance of the fitted values of
`stan_model`

- Calculate the R-squared