add Stan samples

samples/Stan/schools.stan

@@ -0,0 +1,26 @@
+data {
+  int<lower=0> N;
+  vector[N] y;
+  vector[N] sigma_y;
+}
+parameters {
+  vector[N] eta;
+  real mu_theta;
+  real<lower=0,upper=100> sigma_eta;
+  real xi;
+}
+transformed parameters {
+  real<lower=0> sigma_theta;
+  vector[N] theta;
+
+  theta <- mu_theta + xi * eta;
+  sigma_theta <- fabs(xi) / sigma_eta;
+}
+model {
+  mu_theta ~ normal(0, 100);
+  sigma_eta ~ inv_gamma(1, 1); //prior distribution can be changed to uniform
+
+  eta ~ normal(0, sigma_eta);
+  xi ~ normal(0, 5);
+  y ~ normal(theta,sigma_y);
+}