One of the most used statistical techniques is regression analysis. In its simplest (and most used) form, regression analysis is used to describe and analyze the relationship between two continuous variables (e.g., weight and systolic blood pressure). In such instances, each observation (i.e., patient) can be represented with a point in a two-dimensional plot. The analysis is done by assuming that the relationship follows a known mathematical model. The data and the model are displayed in a graph called scatterplot, where x, or explanatory variable, is plotted in the horizontal axis, and y, or response, in the vertical axis. When the model is a straight line (defined by a slope and an intercept) and it is fitted to the data using the method of least ...