 This fact can be shown by calculating the joint probability distribution of the observations and noticing that the resulting formula only depends on which formula_16 values occur among the observations and how many repetitions they each have.Because of this exchangeability, de Finetti's representation theorem applies and it implies that the observations formula_6 are conditionally independent given a (latent) distribution formula_20.This formula_20 is a random variable itself and has a distribution.