Check your understanding of this module before moving on.
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Checkpoint quiz 3 questions
A quick check on this module's key ideas before you move on
Question 01
What does Pipeline.fit() do differently from manually calling fit_transform/transform yourself?
B is correct. A pipeline removes the opportunity for the fit-on-test-data bug entirely, rather than just relying on careful coding to avoid it.
Question 02
What does ColumnTransformer let you do that a single preprocessing step alone cannot?
B is correct. ColumnTransformer routes numeric columns to one transformer (like StandardScaler) and categorical columns to another (like OneHotEncoder), combining the results into one feature matrix.
Question 03
Why can a fitted Pipeline be passed directly into GridSearchCV or cross_val_score?
B is correct. Treating the pipeline as one object means cross-validation refits preprocessing fresh on each fold's training data, avoiding leakage across folds.