The canonical eight schools model generates three stanc warnings:

```
Warning:
The parameter mu has no priors.
Warning:
The parameter tau has no priors.
Warning:
The parameter theta was declared but was not used in the density
calculation.
```

This model is used in the RStan and PyStan documentation. It’s the first model which new users encounter.

I think it would be better if the first model users encounter did not generate warnings.

Here’s the model, for reference:

```
// saved as schools.stan
data {
int<lower=0> J; // number of schools
real y[J]; // estimated treatment effects
real<lower=0> sigma[J]; // standard error of effect estimates
}
parameters {
real mu; // population treatment effect
real<lower=0> tau; // standard deviation in treatment effects
vector[J] eta; // unscaled deviation from mu by school
}
transformed parameters {
vector[J] theta = mu + tau * eta; // school treatment effects
}
model {
target += normal_lpdf(eta | 0, 1); // prior log-density
target += normal_lpdf(y | theta, sigma); // log-likelihood
}
```