Quasi-Experimentation: Design and Analysis Issues for Field Settings — Northwestern ScholarsReprinted from Trochim, W. Editor's Notes. Advances in quasi-experimental design and analysis. The intent of this volume is to update, perhaps even to alter, our thinking about quasi-experimentation in applied social research and program evaluation. Since Campbell and Stanley introduced the term quasi-experiment, we have tended to see this area as involving primarily two interrelated topics: the theory of the validity of casual inferences and a taxonomy of the research designs that enable us to examine causal hypotheses.
Advances in Quasi-Experimentation
In medical studies, usually efficacy studies in experimental settings are conducted to address the issue of internal validity whereas effectiveness studies in naturalistic settings the "real" world are employed to examine the external validity of the claim. Usually patients in experimentation are highly selected whereas patients in the real world are not. For example, subjects in clinical trials usually have just the illness under study. Patients who have multiple health conditions are excluded from the study because those uncontrolled variables could muddle the research results. However, in the real world it is not unusual that patients have multiple illnesses. As a result, a drug that could work well in a lab setting may fail in the real world. Thus, medical researchers must take both internal validity and external validity into account while testing the goodness of a treatment.
Time series methods represent an important research tool for applied social psychologists. Consider interrupted time series designs, in which one assesses the effect of some intervention on an outcome measured repeatedly over time. As one indication of the potential importance of time series methods, consider that Cook and Campbell dedicated two chapters of their book on quasi-experimentation to the topic of interrupted time series, and part of another chapter to methods for assessing the relationship between two ongoing time series.
final de novela tormenta de pasiones