The ideal of the scientist-practitioner as the basis for applied psychology was one of the great achievements of 20th C psychology. Unfortunately, the idea became inextricably linked to the adoption by Psychology of a research methodology (I call it the Standard Model) based on a fusion of the ideas of Fisher and of Neyman and Pearson that are internally incompatible, and poorly adapted to the needs of applied research. Methodological criticism of the Standard Model has grown in intensity and comprehensiveness in the past 50 years. It has been almost completely ignored by researchers. We now have the paradox of applied psychologists, as scientist-practitioners, being expected to conduct evidence-based practice, while researchers themselves persistently ignore the evidence that their methods are flawed. I will review some of this history, and consider some of the ways that we might change our methods to better meet the needs of scientist-practitioners and evidence-based practice. I will particularly discuss the utility of single-case research approaches to applied practice.