Now that you may have built a classification model, there may be many questions going through your mind. For example, suppose you used data from previous sales (training data) to build a classifier to predict customer purchasing behaviour. You would like an estimate of how accurately the classifier can predict the purchasing behaviour of future customers (test data), that is, future customer data on which the classifier has not been trained. You may even have tried different methods to build more than one classifier and now you wish to compare their quality and choose the best one. For this, you will be most interested in the accuracy of the classifier. But

    • What is accuracy?
    • How can we estimate it?
    • Are some measures of a classifier’s accuracy more appropriate than others?
    • How can we obtain a reliable accuracy estimate?

    These questions are addressed in this section.