Question: 1 In this problem, we will empirically verify the ROC curve and the Bayes risk. Consider the following hypothesis problem: H 0 : Y N

1 In this problem, we will empirically verify the ROC curve and the Bayes risk. Consider the
following hypothesis problem: H0 : Y N(0,1) versus H1 : Y N(m,1). Assume uniform costs and the
priors are given by P0 and P1.
(a) Compute the Bayes test. Also specify the expressions of PD, PF and the Bayes risk J in terms of the SNR
parameter d.
(b) Consider three different values of P0={0.1,0.25,0.4} and different values of d ={0,0.1,0.2,,2}. For
each value of P0 and d, generate 106
independent random observation points Y according to the appropriate
prior and conditional distributions (you can use Matlab functions for this). Perform the Bayes test on the
observations and compute the empirical Bayes risk by averaging the risks over all the observations.
(c) Plot the theoretical Bayes risk as a continuous function of d in [0,2]. In the same figure, mark discrete
points (in different color) corresponding to the empirical Bayes risk for d ={0,0.1,0.2,,2}. Repeat the
same exercise in the same figure for all three values of P0={0.1,0.25,0.4}. Comment on what you observe.
1
(d) For each value of d ={1,2,3}, plot the theoretical ROC curve. On the same curve, mark discrete points
(in different color) corresponding to empirical values of PD and PF for each value of P0={0.1,0.25,0.4}.
Comment on what you observe.
(e) You will have to also submit the Matlab code file. The file should run without errors and generate the two
plots in parts (c) and (d). Properly label all the axes, the title of the plot and the legend of the plot. Include
these two figures in the pdf file as well

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