vector<lower=0>[n_classes] alpha_child_level; // variance across recordings for a given child
array[2] vector<lower=0>[n_classes-1] alpha_corpus_level; // variance among children
matrix<lower=0>[n_classes-1,n_corpora] mu_corpus_level; // child-level average
vector<lower=0>[n_classes-1] alpha_pop_level; // variance among corpora
vector<lower=0>[n_classes] mu_pop_level; // population level averages
//vector<lower=0>[n_classes-1] alpha_pop; // mean child-level variance

// siblings
real beta_sib_och; // effect of having siblings on OCH speech
real beta_sib_adu; // effect of having siblings on ADU speech
real<lower=0,upper=1> p_sib; // prob of having siblings


// average effect of age
vector[n_age_bins] d_beta_age;

// effect of excess ADU input
real beta_dev;