Accounting for Nonrandomly Sampled Data in Nonlinear Regression

We analyze data that are "cherry picked" (i.e., nonrandomly sampled) from a population and are then used for regression modeling and prediction. Nonrandom data are encountered in numerous situations, and the application of standard statistical methods developed for random samples can easily lead to incorrect conclusions. A case study is presented to illustrate the related issues, as well as the repercussions of erroneously ignoring the nonrandom sampling.