Stepwise Regression: A Clearer Explanation

In the section of 'Factor Selection', the introduction of stepwise regression method is not clear enough, especially when we only provide the regression equation formula, which is very inappropriate. We have rewritten this section, with a focus on the core idea of this method. As for the detailed steps of this method, the introduction is quite lengthy. We have chosen to reference a literature on method introduction, which provides specific operations for each step in a very clear manner.