Train-Test Split with Stratification: Understanding 'stratify=data['chd']' in Python

The 'stratify' parameter in the train_test_split function in Python is used to specify a column (like 'chd') to perform stratified sampling during data splitting. This ensures that the distribution of this column in the training and testing sets is the same as in the original dataset. This is crucial for problems where certain classes are imbalanced, as maintaining consistent distribution ensures both training and testing sets represent the entire dataset, leading to more accurate evaluation of your model's performance.