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Jingwen · 2022年03月28日

老师,问下对于题目的理解。

NO.PZ2021083101000007

问题如下:

Select performance data from the cross- validation set confusion matrices is presented in Exhibit 1:


Azarov and Bector evaluate the Dataset XYZ performance metrics for Confusion Matrices A, B, and C in Exhibit 1. Azarov says, “For Ganymede’s purposes, we should be most concerned with the cost of Type I errors. ”

Based on Exhibit 1, which confusion matrix demonstrates the most favorable value of the performance metric that best addresses Azarov’s concern?

选项:

A.

Confusion Matrix A

B.

Confusion Matrix B

C.

Confusion Matrix C

解释:

A is correct.

Precision is the ratio of correctly predicted positive classes to all predicted positive classes and is useful in situations where the cost of false positives or Type I errors is high.

Confusion Matrix A has the highest precision and therefore demonstrates the most favorable value of the performance metric that best addresses Azarov’s concern about the cost of Type I errors.

Confusion Matrix A has a precision score of 0.95, which is higher than the precision scores of Confusion Matrix B (0.93) and Confusion Matrix C (0.86).

B is incorrect because precision, not accuracy, is the performance measure that best addresses Azarov’s concern about the cost of Type I errors.

Confusion Matrix B demonstrates the most favorable value for the accuracy score (0.92), which is higher than the accuracy scores of Confusion Matrix A (0.91) and Confusion Matrix C (0.91).

Accuracy is a performance measure that gives equal weight to false positives and false negatives and is considered an appropriate performance measure when the class distribution in the dataset is equal (a balanced dataset).

However, Azarov is most concerned with the cost of false positives, or Type I errors, and not with finding the equilibrium between precision and recall.

Furthermore, Dataset XYZ has an unequal (unbalanced) class distribution between positive sentiment and negative sentiment sentences.

C is incorrect because precision, not recall or F1 score, is the performance measure that best addresses Azarov’s concern about the cost of Type I errors.

Confusion Matrix C demonstrates the most favorable value for the recall score (0.97), which is higher than the recall scores of Confusion Matrix A (0.87) and Confusion Matrix B (0.90).

Recall is the ratio of correctly predicted positive classes to all actual positive classes and is useful in situations where the cost of false negatives, or Type II errors, is high.

However, Azarov is most concerned with the cost of Type I errors, not Type II errors.

F1 score is more appropriate (than accuracy) when there is unequal class distribution in the dataset and it is necessary to measure the equilibrium of precision and recall.

Confusion Matrix C demonstrates the most favorable value for the F1 score (0.92), which is higher than the F1 scores of Confusion Matrix A (0.91) and Confusion Matrix B (0.91).

Although Dataset XYZ has an unequal class distribution between positive sentiment and negative sentiment sentences, Azarov is most concerned with the cost of false positives, or Type I errors, and not with finding the equilibrium between precision and recall.

考点:Model Training - Performance Evaluation

Azarov and Bector evaluate the Dataset XYZ performance metrics for Confusion Matrices A, B, and C in Exhibit 1. Azarov says, “For Ganymede’s purposes, we should be most concerned with the cost of Type I errors. ”

Based on Exhibit 1, which confusion matrix demonstrates the most favorable value of the performance metric that best addresses Azarov’s concern?


就是最关心的是type I error。然后题目问的是:哪个confusion matrix能够最好的表现出Azarov的担忧,不过,显示出来的是最好的值?就是最让他可以不用担忧吗?感觉题目的表述好难理解。

不用担忧就是Precision越接近于1越好,所以是A,是这样吗?

2 个答案
已采纳答案

星星_品职助教 · 2022年03月29日

@Jingwen

根据题干中的“ the most favorable value of the performance metric”,需要选择出1)合适的衡量指标;2)在这个衡量指标里选择最好的值。

根据Azarov说的 “For Ganymede’s purposes, we should be most concerned with the cost of Type I errors. ”可知此时应该选择Precision这个指标。即要看表格中三个Matrix的“precision”列。

而Precision从名字就可以看出,这个指标越大越好。如果从公式分析,如果预测全对了(True Positive,TP),没有错误的(FP),那么这个指标就等于1。所以越靠近1就是most favorable。

所以选择“precision”列里最大的0.95,即Matrix A。

星星_品职助教 · 2022年03月29日

同学你好,

这道题考察的是“当cost of Type I error较高时,采用precision的方式。”。根据题干中的“ we should be most concerned with the cost of Type I errors.”直接选择precision最高的Confusion Matrix A即可。

讲义截图如下:

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2023-04-13 00:16 1 · 回答

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2022-05-29 23:52 1 · 回答

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2021-10-27 23:30 1 · 回答