Linear Regression R-squared (Train): 0.5287297254229243
Linear Regression R-squared (Test): 0.4627146369316367

4-Degree Polynomial Regression R-squared (Train): 0.5895312356444804
4-Degree Polynomial Regression R-squared (Test): 0.4601670183046247

15-Degree Polynomial Regression R-squared (Train): 0.6256705123172766
15-Degree Polynomial Regression R-squared (Test): 0.26972190687190367