The simplest type of regression analysis involves fitting a straight line between two variables (Figure 1). In this case, one of the quantities is called the ''independent or predictor variable'' (usually denoted x), while the other is called the ''dependent or predicted variable'' (usually denoted y). This approach is often referred to as ''simple linear regression,'' or y-on-x regression. It leads to the development of an empirical straight-line relationship between the two variables and has the following form: | The simplest type of regression analysis involves fitting a straight line between two variables (Figure 1). In this case, one of the quantities is called the ''independent or predictor variable'' (usually denoted x), while the other is called the ''dependent or predicted variable'' (usually denoted y). This approach is often referred to as ''simple linear regression,'' or y-on-x regression. It leads to the development of an empirical straight-line relationship between the two variables and has the following form: |