#hybrid-models

Question 1: Single choice

You build a "boosted hybrid" forecaster from a linear regression on trend features and an XGBoost model on other features, such as the month and the product family. Which procedure is right?

Fit the regression to the target, fit XGBoost to its residuals, and add the two predictions1
Fit XGBoost to the target, fit the regression to its residuals, and add the two predictions2
Fit the regression to the target, fit XGBoost to its residuals, and forecast with XGBoost alone3
Fit both models to the target separately and average their forecasts4

Timed test