4. Process Modeling 4.6. Case Studies in Process Modeling 4.6.1. Load Cell Calibration 4.6.1.6. Model Refinement
	After ruling out the straight line model for this data, the next task is to decide what function would better describe the systematic variation in the data.
	Reviewing the plots of the residuals versus all potential predictor variables can offer insight into selection of a new model, just as a plot of the data can aid in selection of an initial model. Iterating through a series of models selected in this way will soon lead to a function that describes the data well.
Residual Structure Indicates Quadratic
	The horse-shoe shaped structure in the plot of the residuals versus load suggests that a quadratic polynomial might fit the data well. Since that is also the simplest polynomial model, after a straight line, it is the next function to consider.