How does bias affect a predictive model?

Bias in a predictive model refers to the error introduced by approximating a real-world problem, which may be complex, using a simplified model. When a model is biased, it simplifies the underlying data patterns and relationships, leading to systematic errors in predictions. This happens because the model fails to capture the intricacies and variability present in the actual data.

A model with high bias tends to make strong assumptions about the data, often resulting in underfitting. This means that it does not learn enough from the training data and therefore performs poorly not only on new, unseen data but even on the training data itself. By oversimplifying the data—often by enforcing rigid structures or relationships—the model is unable to adjust to the true data distribution, thereby creating consistent discrepancies in its predictions.

Understanding the role of bias is crucial, as it directly influences the predictive power and generalization of a model. In this context, a clear recognition of bias allows data scientists to refine their models, ensuring that they appropriately balance complexity and performance for better outcomes.