why random variable is essential why the exchangeability of random variables is essential why is the exchangeability of random variables essential in hierarchical bayesian modeling? why a random variable is essential for hierarchical bayesian modeling? why is the exchangeability of random variables essential? why are random variables essential why are random and exchangeable variables necessary why is exchangeability the essential factor of hierarchical bayesian models why is exchangeability of random variables essential why is the exchangeability of random variables essential in hierarchical bayesian models? why is the exchangeability of random parameters essential why is the exchangeability of random variables essential? why is random variable important for hierarchical bayesian models? why is the exchangeability of random variables essential in hierarchical bayesian modeling? why is the exchangeability of random variable essential in hierarchical bayesian models? why are random variables essential for a hierarchical bayesian model why the exchangeability of random variables is essential in hierarchical bayesian modeling? which is the essential function of hierarchical bayesian models why the exchangeability of random variables is essential in hierarchical bayesian models? why the exchangeability of random variables is essential?