Nonexperimental Designs

Nonexperimental designs include research designs in which an experimenter either simply describes a group or examines relationships between preexisting groups. The members of the groups are not randomly assigned and an independent variable is not manipulated by the experimenter, thus no conclusions about causal relationships between variables in the study can be drawn. Generally, very little attempt is made to control for threats to internal validity in nonexperimental designs. Nonexperimental designs are used simply to answer questions about groups or about whether group [Page 1074]differences exist. The conclusions drawn from nonexperimental research are primarily descriptive in nature. Any attempts to draw conclusions about causal relationships based on nonexperimental research are done so post hoc. This entry begins by clarifying differences between the three primary types ...