Building Machine Learning Systems with Python - Third Edition

Looking behind accuracy – precision and recall

Let's step back and think again about what we are trying to achieve. Actually, we do not need a classifier that perfectly predicts good and bad answers, as we measured it until now using accuracy. If we can tune the classifier to be particularly good at predicting one class, we could adapt the feedback to the user accordingly. If we, for example, had a classifier that was always right when it predicted an answer to be bad, we would give no feedback until the classifier detected the answer to be bad. On the contrary, if the classifier exceeded in predicting answers to be good, we could show helpful comments to the user at the beginning and remove them when the classifier said that the answer is ...