请用中文帮我翻译并回答以下问题Which of the following statements about $k$-Nearest Neighbor ($k$-NN) are true in a classification setting, and for all $k$? Select all that apply. 1. The decision boundary of the k-NN classifier is linear. 2. The training error of a 1-NN will always be lower than or equal to that of 5-NN. 3. The test error of a 1-NN will always be lower than that of a 5-NN. 4. The time needed to classify a test example with the k-NN classifier grows with the size of the training set. 5. None of the above.
时间: 2023-07-15 12:10:28 浏览: 73
以下哪些关于$k$-最近邻($k$-NN)在分类问题中的说法是正确的,并且对于所有的$k$都适用?请选择所有正确的说法。1. $k$-NN分类器的决策边界是线性的。2. 1-NN的训练误差总是低于或等于5-NN的训练误差。3. 1-NN的测试误差总是低于5-NN的测试误差。4. 使用$k$-NN分类器对一个测试样本进行分类所需的时间会随着训练集的大小增加而增加。5. 以上说法均不正确。
正确答案是2和4。2是正确的,因为1-NN是完全依赖训练数据的,因此它的训练误差应该是最小的。4是正确的,因为使用$k$-NN分类器对每个测试样本进行分类时,都需要计算与所有训练样本之间的距离,因此随着训练集的大小增加,所需的时间也会增加。1、3、5都是不正确的。
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