A model starts with a decision, not an algorithm.
A sales team wants to call customers likely to accept an offer. One row is one eligible customer. The target is whether the customer accepts. Features must be available before the call. Information recorded afterward cannot help a real prediction.
This is supervised learning: examples pair inputs with known outcomes so a model can learn a mapping used on new examples.[1]
A baseline sets the minimum useful score. For classification, predict the most frequent class. If 9% accept, always predicting “no” gets 91% accuracy and zero useful leads. High accuracy can still be worthless.
Read the opening module of the scikit-learn MOOC. Keep the workflow sheet beside later lessons.