During which stage in the Foundational Data Science Methodology is a test data set used for model evaluation?

A test dataset is specifically utilized in the Model Evaluation stage of the Foundational Data Science Methodology. This is the phase where the performance of the model is assessed using unseen data, which the model has not been trained on. By evaluating the model on this test dataset, practitioners can measure its accuracy, performance metrics, and generalization ability.

Using a test dataset is crucial because it provides insights into how the model might perform in real-world scenarios, ensuring that the insights gained are not just a result of overfitting to the training data. This evaluation helps in determining whether the model meets the necessary criteria to be deployed for practical use.

In other stages such as Data Requirements or Analytic Approach, the focus is on understanding the data needed and developing the algorithms to be used, rather than on evaluating the model's performance. The Deployment stage occurs after the model has been tested and validated, involving the actual implementation of the model in a live environment.