Likelihoods

BernoulliProdLik([link])	Product of Bernoulli likelihoods.
BinomialProdLik(ntrials[, link])	Product of Binomial likelihoods.
DeltaProdLik([link])	Product of Kronecker delta likelihoods.
PoissonProdLik([link])	Product of Poisson likelihoods.