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k-NN: This problem derives a performance bound on the 1-NN classifier. Consider the 1-NN binaryclassifier on a two-dimensional space. For an input x and its nearest neighbor xn in the trainingdata, the conditional probabilities of belonging to classes c1 and c2 are as follows:◦ p(c1|x) : probability that x belongs to c1◦ p(c2|x) : probability that x belongs to c2◦ p(c1|xn) : probability that xn belongs to c1◦ p(c2|xn) : probability that xn belongs to c2Knowing that p(c1|x) + p(c2|x) = 1 and p(c1|xn) + p(c2|xn) = 1,(a) Express the conditional probability of misclassification error, e, for x, P (e|x, xn), in terms ofthe probabilities provided above.

Question

k-NN: This problem derives a performance bound on the 1-NN classifier. Consider the 1-NN binaryclassifier on a two-dimensional space. For an input x and its nearest neighbor xn in the trainingdata, the conditional probabilities of belonging to classes c1 and c2 are as follows:◦ p(c1|x) : probability that x belongs to c1◦ p(c2|x) : probability that x belongs to c2◦ p(c1|xn) : probability that xn belongs to c1◦ p(c2|xn) : probability that xn belongs to c2Knowing that p(c1|x) + p(c2|x) = 1 and p(c1|xn) + p(c2|xn) = 1,(a) Express the conditional probability of misclassification error, e, for x, P (e|x, xn), in terms ofthe probabilities provided above.

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Solution

The conditional probability of misclassification error, e, for x, P(e|x, xn), can be expressed in terms of the probabilities provided above as follows:

P(e|x, xn) = P(c1|x)P(c2|xn) + P(c2|x)P(c1|xn)

This equation represents the probability that x is classified incorrectly given its nearest neighbor xn. The first term on the right, P(c1|x)P(c2|xn), represents the probability that x belongs to class c1 but its nearest neighbor xn belongs to class c2. The second term, P(c2|x)P(c1|xn), represents the probability that x belongs to class c2 but its nearest neighbor xn belongs to class c1. In both cases, the 1-NN classifier would make a misclassification error.

This problem has been solved

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