#target-leakage

Question 1: Single choice

A model predicts how many shoelaces a shoe company will need each month. Its features are the month, last month's advertising spending, economic indicators at the start of the month, and the amount of leather used during the month. With the leather feature it is almost perfectly accurate. When is that feature a source of target leakage?

When the leather amount is only known after the prediction is made1
Always, because leather and shoelaces both follow from the number of shoes produced2
Never, because leather is a different material from shoelaces3
Only if the model is validated with cross-validation instead of a hold-out set4

Timed test