Nonexperimental Designs

Measurement of Assumed Causes

In nonexperimental research, variables that are assumed causes are measured, as opposed to being manipulated. For example, a researcher interested in testing the relation between organizational commitment (an assumed cause) and worker productivity (an assumed effect) would have to measure the levels of these variables. Because of the fact that commitment levels were measured, the study would have little if any internal validity. Note, moreover, that the internal validity of such research would not be at all improved by a host of data analytic strategies (e.g., path analysis, structural equation modeling) that purport to allow for inferences about causal connections between and among variables (Stone-Romero, 2002; Stone-Romero & Rosopa, 2004).

Nonrandom Assignment of Participants and Absence of Conditions

In nonexperiments, there are typically no explicitly defined research conditions. For example, a researcher interested in assessing the relation between job satisfaction (an assumed cause) and organizational commitment (an assumed effect) would simply measure the level of both such variables. Because participants were not randomly assigned to conditions in which the level of job satisfaction was manipulated, the researcher would be left in the uncomfortable position of not having information about the many variables that were confounded with job satisfaction. Thus, the internal validity of the study would be a major concern. Moreover, even if the study involved the comparison of scores on one or more dependent variables across existing conditions over which the researcher had no control, the researcher would have no control over the assignment of participants to the conditions. For example, a researcher investigating the assumed effects of incentive systems on firm productivity in several manufacturing firms would have no control over the attributes of such systems. Again, this would serve to greatly diminish the internal validity of the study.

Measurement of Assumed Dependent Variables

In nonexperimental research, assumed dependent variables are measured. Note that the same is true of both randomized experiments and quasi-experiments. However, there are very important differences among the three experimental design types that warrant attention. More specifically, in the case of well-conducted randomized experiments, the researcher can be highly confident that the scores on the dependent variable(s) were a function of the study's manipulations. Moreover, in quasi-experiments with appropriate design features, the investigator can be fairly confident that the study's manipulations were responsible for observed differences on the dependent variable(s). However, in nonexperimental studies, the researcher is placed in the uncomfortable position of having to assume that what he or she views as dependent variables are indeed effects. Regrettably, in virtually all nonexperimental research, this assumption rests on a very shaky foundation. Thus, for example, in a study of the assumed effect of job satisfaction on intentions to quit a job, what the researcher assumes to be the effect may in fact be the cause. That is, individuals who have decided to quit for reasons that were not based on job satisfaction could, in the interest of cognitive consistency, view their jobs as not being satisfying.

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