问题
*Hi again i am in problem for comparing confusion matrix. Bellow i have provided the two confusion matrix.
a b classified as
349 58 a tested_negative
93 124 b tested_positive
a b classified as
346 61 a tested_negative
90 127 b tested_positive
i know that the diagonal of top-left to right but here both that value is same so how can i make decision which one best?*
回答1:
It actually depends on your specific application. Say you want to minimize number of false positives (because it will cost you a lot to deal with consequences of any false alarm)
In this case, choose the first classifier, because its false positive rate is less then that of the second classifier:
58/(58+124) < 61/(61+127) 0.3186813 < 0.3244681
Take a look here http://en.wikipedia.org/wiki/Accuracy_and_precision
and here: http://en.wikipedia.org/wiki/Sensitivity_and_specificity
If you just want "the best classifier" - you have a problem, since both classifiers have the same accuracy:
a1 = (349+124)/(349+124+58+93) = 0.7580128 a2 = (346+127)/(346+127+61+90) = 0.7580128
So you need to analyze your domain or industry and decide whether you want to:
1) get as little false alarms as possible - then choose classifier with minimum false positive rate;
2) get as little missed cases as possible - then choose classifier with minimum false negative rate;
3) get more hits as possible - then choose classifier with maximum true positive rate;
4) get more correct rejections - then choose classifier with maximum true negative rate.
来源：https://stackoverflow.com/questions/23104503/weka-software-analysis-of-confusion-matrix