1.I.7H1 . \mathrm{I} . 7 \mathrm{H} \quad

Statistics
Part IB, 2008

A Bayesian statistician observes a random sample X1,,XnX_{1}, \ldots, X_{n} drawn from a N(μ,τ1)N\left(\mu, \tau^{-1}\right) distribution. He has a prior density for the unknown parameters μ,τ\mu, \tau of the form

π0(μ,τ)τα01exp(12K0τ(μμ0)2β0τ)τ,\pi_{0}(\mu, \tau) \propto \tau^{\alpha_{0}-1} \exp \left(-\frac{1}{2} K_{0} \tau\left(\mu-\mu_{0}\right)^{2}-\beta_{0} \tau\right) \sqrt{\tau},

where α0,β0,μ0\alpha_{0}, \beta_{0}, \mu_{0} and K0K_{0} are constants which he chooses. Show that after observing X1,,XnX_{1}, \ldots, X_{n} his posterior density πn(μ,τ)\pi_{n}(\mu, \tau) is again of the form

πn(μ,τ)ταn1exp(12Knτ(μμn)2βnτ)τ\pi_{n}(\mu, \tau) \propto \tau^{\alpha_{n}-1} \exp \left(-\frac{1}{2} K_{n} \tau\left(\mu-\mu_{n}\right)^{2}-\beta_{n} \tau\right) \sqrt{\tau}

where you should find explicitly the form of αn,βn,μn\alpha_{n}, \beta_{n}, \mu_{n} and KnK_{n}.