data {
  int N;
  vector[N] x;
  int y[N];
  real df;
}
parameters {
  real a;
  real b;
}
model {
  vector[N] p;
  for (n in 1:N) p[n] = student_t_cdf(a + b*x[n], df, 0, sqrt((df - 2)/df));
  y ~ bernoulli(p);
}