00:01
For this question, we have to answer parts 1 and 2.
00:05
So for part 1, it asks, what is the bayes decision boundary? so the bayes decision boundary is the boundary that separates the two classes and minimizes expected loss.
00:39
So in this case, the expected loss is given by l equals p times w1 times p error of w1 plus p of w2 times the p error of w2.
01:07
So where p error of w1 is the probability of error given that the true class is w1.
01:18
So using the bayes rule, we can compute the posterior probabilities as follows, which would be p of w2 x, which equals p x of w2 times p of w2 divided by p x of w1 times p of w1 plus p of x of w2 times p w2.
02:07
So plugging in the given values, we get p w1 equals 1 divided by 3 divided by 1 divided by 3 plus 2 divided by 15 times exponential x minus 1 to the power of 2 divided by 8.
02:37
So that would simplify to w p of w2 equals 2 divided by 15 times the exponential of x minus 1 to the power of 2 divided by 8 divided by 1 divided by 3 plus 2 divided by 15.
03:10
So now to minimize the expected loss, we should choose the class with the highest posterior for each value of x.
03:20
So the decision boundary is given as p of w1 equals p of w2...