Regression analysis is a statistical process for estimating the relationship between two or more variables. The relationship is modeled as $$y \sim x$$ or $$y = f(x)$$. Both model descriptions indicate, that the variable $$y$$ is a function of $$x$$. Therefore, the variable $$y$$ is denoted as the response variable or dependent variable, whereas the variable $$x$$ is denoted as the predictor variable or independent variable.