Graphics
Model: y = f(x;beta) + e   =  beta(1)exp[-beta(2)x] + beta(3)exp[-(x - beta(4)^2 / beta(5)^2 + beta(6)exp[-(x - beta(7)^2 / beta(8)^2] + e

Fitted and Observed Values
versus
Predictor Variable


Fitted and Observed Values vs. Predictor Variable
Residuals
versus
Predictor Variable


Residuals vs. Predictor Variable