Define key metrics of model performance

It is important to anticipate how you will measure the performance of the model. Start thinking about the metric or metrics you plan to use to measure the performance of the model, and most importantly why these metrics are relevant for the problem at hand. We will talk in depth about model evaluation and the different metrics in Chapter 7, Model Evaluation.

A word of advice: Don't promise anything about the performance of your model; don't say things like, "I am confident we can get above 95% accuracy," because you do not know ahead of time how good the model will be.