ISYE 6501 Midterm 2 Exam questions and answers Graded A+ latest update Main reasons to limit number of factors in model - Overfitting - when # of factors is close to or larger than # of data points; Simplicity - simple models are better; reduce the nu

ISYE 6501 Midterm 2 Exam questions and answers Graded A+ latest update Main reasons to limit number of factors in model - Overfitting - when # of factors is close to or larger than # of data points; Simplicity - simple models are better; reduce the number of correlated variables; certain variables might be hard to collect data or expensive; some variables are missing data or hard to use Why are simple models better? - Less data is required, less chance of insignificant factors, easier to interpret Examples of factors that are illegal to use - race, sex, religion, marital status, or any factors that are highly correlated with forbidden ones What is forward selection? - Start with a model with no factors, at each step, find each best new factor to add to model, and put it in if good enough (parameter of your choice like p value=0.15) improvement; when there is no factor that is good enough or if we add enough factors, we stop; can remove any factors at the end What is backward selection? -