Evaluation of the choice of design and the author’s rationale for the design choice
A quasi-experimental design is a design which is commonly used when it is impossible to implement the methods of experimental design. Such kind of design can be helpful in social, educational and behavioral research. One of the main peculiarities of quasi-experimental design which explains its credibility and spread in the experimental world is the possibility to conduct research in real world circumstances and take into consideration the impacts from different fields that cannot be predicted. The examples of how a quasi-experimental design may be applied are perfectly observed in the articles by Bartholomew et al. (2008), who admit that the chosen design helped to consider even small changes in behavior of the participants and achieve the required results, and DeBourdeaudhuij et al. (2007), who proved that the chosen design could be applied for large scale dissemination. Frankfort-Nachmias and Nachmias (2007) define quasi-experimental design as the only appropriate study where more than one sample may be taken into consideration over a certain period of time. This is why the choice of the design by the authors of the articles is clear enough: with the help of this design, it is possible to use large scales of the experiments as well as to rely on the conditions, which are inherent to the real world.
The types of validity, critical differences among them, and the author’s performance in explaining them
Being a successful research deign for the experiments developed by Bartholomew et al. or DeBourdeaudhuij et al, a quasi-experimental design is characterized by a number of threats validity. These threats may vary considerably: construct, convergent, conclusion, external, criterion, predictive, concurrent, face, etc. The threads to validity are usually expresses via inappropriate selection of measurements or the collection of irrelevant data. Crewswell (2003) says that there are two important types of variables in any kind of research, dependent and independent, and if a mistake takes place, the development of the investigation may be under a threat. This is why, choosing this or that research design, a researcher should do everything possible to reduce the threats to validity to minimum, especially internal ones. For example, in Bartholomew et al. project (2008), it is identified that “the failure to obtain a standardized frequency of delivery likely lessoned the impact of the intervention” may provide a threat to internal validity (p. 302).
The study’s validity evaluation
Quantitative research designs have a number of advantages and disadvantages along with other peculiarities. A choice of a quantitative research design depends on the main idea of the study and the results which are desired to be achieved. The examples discussed above help to understand that study’s validity may depend on different factors, this is why the researchers should pay more attention to the designs, which promote the reduction of threats to validity. And one of the most credible ideas is considered to be a quasi-experimental design with the help of which some measurements may be re-established and pre- or post-tests can be administrated. This is why if there is a chance to use some combine methods, it is better to use it and try to achieve the best possible results. There are a number of external and internal factors, which may define the quality of the research conducted, and the idea to use the designs and reduce of threats to validity or measure the variables.
Reference List
Bartholomew, J., Miller, B., Ciccolo, J., Atwood, R., & Gottlieb, N. (2008). Walk Texas! 5-a-day intervention for Women, Infants, and Children (WIC) clients: A quasi-experimental study. Journal of Community Health, 33, 297–303.
Crewswell, J. (2003). The purpose statement. Research design: Qualitative, quantitative, and mixed methods approaches. Thousand Oaks: Sage Publications.
DeBourdeaudhuij, I., Stevens, V., Vandelanoote, C., & Johannes, B. (2007). Evaluation of an interactive computer-tailored nutrition intervention in a real-life setting. Annals of Behavioral Medicine, 33(1), 39–48.
Frankfort-Nachmias, C. & Nachmias, D. (2007). Cross-sectional and quasi-experimental research designs. Research methods in the social sciences. New York: Worth Publishers.