More Complex Relationships
This chapter is concerned with more complex relationships estimated in different environments and with examining the possible dependence of y on several x variables. The y variable is called the dependent variable and the x variables are called independent variables. The chapter considers the situation where the relationship between y and x is not linear, that is, cannot be represented by a straight line. Multiple regression is a very powerful tool for investigating relationships. The chapter describes the principles and illustrates the use of multiple regression. The calculations for fitting multiple regression will inevitably involve the use of a computer package. More complex regression techniques, known as weighted regression, can be used if the transformation to linearity has not also achieved a constant variance. Even the computer can experience computational difficulties in multiple regression fitting and the users of multiple regression programs should beware of the computational problems that may arise.