Asked about Shaping inputs so the model can use them
A feature makes your model far more accurate than expected. What do you check?
An answer that works
Whether it leaks. Is it populated only after the outcome is known, does it correlate with the label through how the data was ordered, is it an aggregate computed over the whole dataset. The test is whether it would genuinely be available with that value at prediction time.
Reading an answer is not being able to give one. The section that teaches this is Shaping inputs so the model can use them, 6 hours of Feature engineering.
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