What are the resources needed by clinical pharmacology to test drugs in ways that model how the practitioner achieves optimal effectiveness and safety with each patient? I describe the applications of test-retest standard error of measurement, clinical decision rules, means or other statistical summaries of observations, clinical trial designs that use each patient as her own control, and methods to control observer and site variance as steps for developing a CT tested model for optimal clinical uses of an Alzheimers drug by a practitioner. Many investigators and clinicians have been concerned with clinical judgments being scientifically uncontrolled and unsystematic. The methods I describe demonstrate how clinical trials can be used to overcome these limitations in current patient care. “Darwin showed that one simply could not understand evolution as long as one accepted essentialism. Species and populations are not types, they are not essentialistically defined classes, but rather are biopopulations composed of genetically unique individuals” E. Mayr .