model {
   for (i in 1:BATCHES) {
      for (j in 1:SAMPLES) {
         y[i,j] ~ dnorm(mu[i], tau.within);
      }
      mu[i] ~ dnorm(theta, tau.between);
   }

   theta ~ dnorm(0.0, 1.0E-10);
   tau.within ~ dgamma(0.001, 0.001);  sigma2.within <- 1/tau.within;
   tau.between ~ dgamma(0.001, 0.001);  sigma2.between <- 1/tau.between;
   
   sigma2.total <- sigma2.within + sigma2.between;
   f.within <- sigma2.within/sigma2.total;     
   f.between <- sigma2.between/sigma2.total;     
}