As we have seen throughout this book, ML is highly dependent on the data that is used for training and testing. For this reason, we find it helpful to view a typical project through the stages in the following diagram, which comes from the Cross Industry Standard Process for Data Mining (CRISP-DM), a popular method for managing data science projects[3]:
In contrast to some other engineering systems, ML normally never produces perfect output, so, for this reason, projects are often iterative. Refinements to the datasets and models allow you to produce progressively better results, provided they are justified by your business needs.