Possible data leakage: transformations fitted on test data

[Shraddha6211]

Hi! Thanks for the great tutorial, it was very helpful.

I noticed that during column transformations in Aam Zindagi portion, the test data is also being fitted
(e.g., using fit_transform on test data instead of only transform).

This could lead to data leakage, since test data should only be transformed using
parameters learned from the training https://github.com/campusx-official/100-days-of-machine-learning/blob/main/day28-column-transformer/day28.ipynb

Would it be better to:

• fit transformations on training data only, and
• apply transform on test data
  (possibly using a Pipeline / ColumnTransformer)?

Just wanted to point this out in case it helps future learners