What is a Confusion Matrix in Machine Learning - Machine Learning Mastery

This matrix can be used for 2-class problems where it is very easy to understand, but can easily be applied to problems with 3 or more class values, by adding more rows and columns to the confusion matrix. Let's make this explanation of creating a confusion matrix concrete with an example. Let's pretend we have a two-class classification problem of predicting whether a photograph contains a man or a woman. We have a test dataset of 10 records with expected outcomes and a set of predictions from our classification algorithm. Let's start off and calculate the classification accuracy for this set of predictions. The algorithm made 7 of the 10 predictions correct with an accuracy of 70%. First, we must calculate the number of correct predictions for each class. Now, we can calculate the number of incorrect predictions for each class, organized by the predicted value.