Regression analysis looks at data from engineering experiments to find the best way to represent it. It helps us understand how one thing affects another and uses different methods like linear, polynomial, and non-linear regression. By fitting data to models, we can see how well they match reality. Scientists test these models using correlation and X2 tests to see if they're accurate. The idea is that errors in the data should follow a pattern. By using least square analysis, we can estimate how well our models fit the data. In simpler terms, regression analysis helps us make sense of how variables relate in real-world situations.