The experiment is an essential element of any given research problem. The experiment can take various forms and designs with a quasi-experimental design being one of the most common experimental designs. According to Kontopantelis et al., (2015), a quasi-experimental design is an experiment that resembles a typical experiment in most aspects but lacks this vital element of an experimental set-up. Such an experimental set-up may be referred to as queasy experiment because they instill a queasy feeling in experiment purists. The internal validity of quasi-experiments always tends to be weaker as contrasted with other experimental designs.
The key merit of quasi-experimental designs is their ease of frequent implementation as opposed to their randomized counterparts. A quasi-experimental design can be summarized as an experiment without randomization (Donofrio et al., 2013). Many experiment purists regard this method as unreliable and unscientific. Physical and biological scientists refute the legitimacy of this method, but it is an important element of research involving a social variable. A quasi-experimental does not include random allocation of groups, which is very vital in establishing sound statistical analysis. This paper discusses the ways for ensuring high internal validity in a quasi-experimental design educational research.
Campbell and Stanley (2015) note that ensuring high internal validity in a quasi-experiment is a difficult task to most researchers. In an experimental design, internal validity is the extent of the reliability of the outcome of an experiment. This is a measure of how well an experiment has been conducted and must not be confounding in its results. The independent variable in an experimental design must be only one to minimize chances of confounding in an experiment. In a quasi-experimental design, the variable is tested in groups, which are not randomized during preselecting. Educational research is a vital way of obtaining systematic and analyzed data on various aspects of education such as psychology, philosophy, anthropology, and sociology (Gay, & Mills, 2015). Most researchers expect that the methods employed in the attainment of the experimental inference should be rigorous and follow systematic ways.
According to Hessel, Vandoros, and Avendano (2014), the key threat to internal validity in a quasi-experiment is ambiguity in the independent and dependent variable in an experiment and confounding. They state that a working remedy for this threat is clear indication of the variable and a complete definition of each variable concerning the identity as a dependent or independent variable in the experimental design. The experimenter should be in a position to formulate the objective of the experiment. This makes the variable tested against another be defined, and the expected form of the result be noted. Therefore, a researcher is in a good position to demarcate the causative agents in an experimental outcome and the underlying effects. This is the foundation of a reliable conclusion.
History is another threat to internal validity in an experiment. History is any unplanned events that occur while the study is in progress and interferes with the outcome of a study. When a pre-test and post-test is done on two different groups such as a classroom before and after a lesson, events during the lesson may interfere with the outcome. Laying appropriate measures so that experiment groups are kept under similar conditions and all variables, which are not in question, are kept unchanged is thus essential.
During an experiment, biological and psychological changes may occur within the participants (Geyer, Haan, & Wrohlich, 2015). Similarly, experiments previously done on the participants may influence their performance. The fact that the subjects would have been exposed to the expected test makes them give different results to fit what they feel should be the given. It is important to avoid redundancy of research and exploring participants who have not been suggested to the same research for the best of the experiment results. It is also important to ensure that the participants are not bored, tired or hungry to eliminate any possible element of maturation.
Human observation and perception is the key instrument during an educational experiment. Instrumentation in an educational experiment would entail any change that would alter the perception and observation of time. A researcher should ensure that the instruments involved in the experiment and this case, the human perception and observations remain unaltered. The approach a researcher uses may influence the ideology of a participant and make them present biased views (Sommers, Long, & Baicker, 2014). This is likely to cause great statistical regression, especially where a pretest and post-test are involved.
Conclusively, a quasi-experimental design is a very vital part of educational research. Internal validity in educational research is vital and need to be considered. The threats to internal validity, which vary from variable ambiguity to history and selection interaction, are points of great concern. A good choice of experimental procedure and understanding of the variables involved in the research are significant for the attainment of high internal validity. Moreover, the experimenter should consider methods that do not affect the perception of the participants and have an influence on their observation.
Campbell, D. T., & Stanley, J. C. (2015). Experimental and quasi-experimental designs for research. Ravenio Books
Donofrio, B. M., Lahey, B. B., Turkheimer, E., & Lichtenstein, P. (2013). Critical need for family-based, quasi-experimental designs in integrating genetic and social science research. American journal of public health, 103(S1), S46-S55
Gay, L. R., & Mills, G. E. (2015). Educational Research: Competencies for Analysis and Applications, Global Edition: Edition 11. Pearson Education Limited
Geyer, J., Haan, P., & Wrohlich, K. (2015). The effects of family policy on maternal labor supply: Combining evidence from a structural model and a quasi-experimental approach. Labour Economics, 36, 84-98
Hessel, P., Vandoros, S., & Avendano, M. (2014). The differential impact of the financial crisis on health in Ireland and Greece: a quasi-experimental approach. Public health, 128(10), 911-919
Kontopantelis, E., Doran, T., Springate, D. A., Buchan, I., & Reeves, D. (2015). Regression based quasi-experimental approach when randomisation is not an option: interrupted time series analysis. bmj, 350, h2750
Sommers, B. D., Long, S. K., & Baicker, K. (2014). Changes in Mortality After Massachusetts Health Care ReformA Quasi-experimental StudyChanges in Mortality After Massachusetts Health Care Reform. Annals of internal medicine, 160(9), 585-593
Vandoros, S., Hessel, P., Leone, T., & Avendano, M. (2013). Have health trends worsened in Greece as a result of the financial crisis? A quasi-experimental approach. The European Journal of Public Health, 23(5), 727-731
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