ABSTRACT
Scientists are frequently interested in studying the functional relationship between two variables y and x. For example, in an agricultural experiment, the crop yield y may depend on the amount of fertilizer x; in a metallurgical experiment one is interested in the shear strength y of a spot weld as a function of the weld diameter x. The variable x is variously called the explanatory variable, the regressor variable, or the predictor variable; y is called the dependent variable and also the response variable.
