We define a conjugate prior for the reversible Markov chain of order r. The
prior arises from a partially exchangeable reinforced random walk, in the same
way that the Beta distribution arises from the exchangeable Poly\'{a} urn. An
extension to variable-order Markov chains is also derived. We show the utility
of this prior in testing the order and estimating the parameters of a
reversible Markov model.Comment: Published in at http://dx.doi.org/10.1214/10-AOS857 the Annals of
Statistics (http://www.imstat.org/aos/) by the Institute of Mathematical
Statistics (http://www.imstat.org