o use a non-centered parameterization
is the only way to correct these problems.
In this second model, the parameters <code>x_raw</code> and <code>y_raw</code> are sampled as independent
standard normals, which is easy for Stan.</p>
<pre><code>parameters {
  real y_raw;
  vector[9] x_raw;
}
transformed parameters {
  real y;
  vector[9] x;

  y = 3.0 * y_raw;
  x = exp(y/2) * x_raw;
}
model {
  y_raw ~ std_normal(); // implies y ~ normal(0, 3)
  x_raw ~ std_normal(); // implies x ~ normal(0, exp(y/2))
}</co