Model evaluation in machine learning

Model evaluation is a crucial aspect of the machine learning (ML) development pipeline, often misunderstood by practitioners eager to deploy models quickly. Despite the allure of aggregate metrics like accuracy, these measures can provide a misleading picture of a model's performance, as they compress complex behaviors into single numbers and may not account for performance across different data subsets. The generalization capacity of a model, which predicts performance on new data, is typically estimated using methods such as cross-validation or holdout datasets, but these methods have limitations and can lead to over-reliance on benchmarks. The text emphasizes the importance of examining model performance across various cohorts to avoid potential biases and ensure ethical application, particularly in high-stakes scenarios like recidivism prediction, where models have shown disparate accuracy across different ethnic groups. It warns against the pitfalls of trusting solely in metrics without understanding their limitations and encourages a more comprehensive approach to model evaluation, such as the tools developed by Openlayer, which facilitate thorough testing and validation.