A data scientist is using SageMaker to train a model on a dataset with many features. They suspect some features are redundant. Which feature engineering technique would help?
PCA reduces dimensionality by transforming correlated features into uncorrelated components, eliminating redundancy.
Why this answer
Principal Component Analysis (PCA) is a dimensionality reduction technique that transforms the original correlated features into a smaller set of uncorrelated principal components, effectively removing redundancy while preserving most of the variance in the data. In SageMaker, PCA can be applied via the built-in PCA algorithm or as a preprocessing step in a scikit-learn container to reduce feature space and eliminate multicollinearity.
Exam trap
The AIF-C01 exam often tests the distinction between feature reduction (PCA) and feature transformation (scaling, encoding, polynomial expansion) to see if candidates confuse techniques that change feature count versus those that only change feature values.
How to eliminate wrong answers
Option A is wrong because feature scaling (e.g., StandardScaler, MinMaxScaler) normalizes the range of features but does not remove redundant or correlated features; it only changes the scale. Option B is wrong because one-hot encoding is used to convert categorical variables into numerical format, not to address feature redundancy among many continuous or numerical features. Option D is wrong because polynomial features create interaction and higher-order terms, which actually increase the number of features and can introduce more redundancy, not reduce it.