Special Issues in Subject Selection and Design
Subject selection is a critical procedure for all psychology research. Except under unusual circumstances, subject characteristics cannot be altered for the purpose of experimental manipulation. Therefore, effective subject selection is essential in assuring at least quasi-experimental status for most of our studies in psychology. Furthermore, the complex and dynamic nature of the human personality carries the potential for confounding effects likely to obscure the meaning of research results. Judicious subject selection is important in reducing experimental error. There is no question that reliability and validity, as well as generalizability, depend to a large extent on appropriate subject selection.