Quasi-Experimental Design - Experiments without randomizationThe experimental and quasi-experimental designs refer to the research papers. While experimental designs mean the entirely controlled experiment, different types of quasi-experimental design may imply the lack of such control. For example, the experimental design is used in the psychological research paper where the researcher can lead the experimental group, its population, and actions of every member. Types of quasi-experimental design are combined by the absence of one or several key features of a true design: control, random choice or random treatment. A quasi-experimental design may be applied in the majority of natural sciences where the members and factors cannot be fully controlled.
Quasi-Experiments vs True Experiments
Quasi-experimental study designs, often described as nonrandomized, pre-post intervention studies, are common in the medical informatics literature. Yet little has been written about the benefits and limitations of the quasi-experimental approach as applied to informatics studies. This paper outlines a relative hierarchy and nomenclature of quasi-experimental study designs that is applicable to medical informatics intervention studies. In addition, the authors performed a systematic review of two medical informatics journals, the Journal of the American Medical Informatics Association JAMIA and the International Journal of Medical Informatics IJMI , to determine the number of quasi-experimental studies published and how the studies are classified on the above-mentioned relative hierarchy. They hope that future medical informatics studies will implement higher level quasi-experimental study designs that yield more convincing evidence for causal links between medical informatics interventions and outcomes.
An experiment is a study in which the researcher manipulates the level of some independent variable and then measures the outcome. Experiments are powerful techniques for evaluating cause-and-effect relationships. Many researchers consider experiments the "gold standard" against which all other research designs should be judged. Experiments are conducted both in the laboratory and in real life situations. True experiments, in which all the important factors that might affect the phenomena of interest are completely controlled, are the preferred design. Often, however, it is not possible or practical to control all the key factors, so it becomes necessary to implement a quasi-experimental research design. In an experiment, the researcher manipulates the factor that is hypothesized to affect the outcome of interest.
Threats to internal validity in designs with control groups. Selection reserved to describe the non-intervention group in a quasi-experimental design.
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Quasi-experimental design is a form of experimental research used extensively in the social sciences and psychology. Whilst regarded as unscientific and unreliable , by physical and biological scientists, the method is, nevertheless, a very useful method for measuring social variables. The inherent weaknesses in the methodology do not undermine the validity of the data, as long as they are recognized and allowed for during the whole experimental process. Quasi experiments resemble quantitative and qualitative experiments , but lack random allocation of groups or proper controls, so firm statistical analysis can be very difficult. Quasi-experimental design involves selecting groups, upon which a variable is tested, without any random pre-selection processes. For example, to perform an educational experiment, a class might be arbitrarily divided by alphabetical selection or by seating arrangement. The division is often convenient and, especially in an educational situation, causes as little disruption as possible.