Ronald D. Franklin, PhD Center for Forensic and Neuropsychology, Boca Raton FL Saint Mary's Hospital, West Palm Beach FL
David B. Allison, PhD Obesity Research Center St. Luke's/Roosevelt Hospital Center Columbia University College of Physicians and Surgeons
Bernard S. Gorman, PhD Nassau Community College Hofstra University
Scientific knowledge includes two paths, deductive reasoning and inductive reasoning. The former involves logical proofs and deductions and is not the subject of this volume. The latter involves drawing inferences from experiences and empirical data. Within the empirical method, there are both observational (sometimes called correlational) studies and experimental studies. Although both kinds of studies are essential to scientific progress, experimental studies generally play a greater role in the evaluation of interventions and therefore are the primary (although not exclusive) focus of this book.
Some authors reserve the term experiment for those studies in which experimenters assign observations randomly to different levels of the treatment (independent variable). Here, we use the term in a more liberal sense by defining an experiment as any study in which the experimenter manipulates the independent variable, even if assignment is not random.
Virtually all scientists and most clinicians have had at least one course in research methods and in that course have learned a bit about experi-