$20m249$ ssep.dvi

M$249$ Exam $2024$

c$2$b$00121$e$904$f$904$e$1?$response$-$content$-$disposition$=$inline$\%3$Bfilename$\%3$D$"$M$249$

$21/21$

$90\%$

Question $24$

WinBUGS was used to sample from a posterior distribution for a parameter $.$ Two chains of sampled values, each of $4000$ iterations, were obtained. A trace plot for the two chains superimposed on the same diagram is shown in Figure $12.$

Figure $12$

Alison and Bill disagree on how many iterations in the samples should be disregarded. Bill argues that it is sufficient to disregard the first $1800$ iterations, whereas Alison argues that at least $2800$ iterations need to be disregarded. Who is right? Justify your answer.

$[$END OF QUESTION PAPER$]$