Dear professors,
What is the minimum sample size for a quasi experment if I want to conduct a study on the effects of the instruction on students' receptive skills. Can I have two intact classes including a experimental group with 20 students and a control group with 25 students respectively? Can I have the similar participants numbers with similar characteristics in my pilot study? Would you please provide me some good papers mentioning this sample size? Thank you very much.
Determining the minimum sample size for a quasi-experimental study depends on several factors, including the desired statistical power, effect size, and significance level. Generally, the larger the sample size, the more precise the estimates will be. However, it is often difficult to obtain large sample sizes in educational research.
One study, published in "Characterising and justifying sample size sufficiency in interview-based studies", suggested that a sample size of at least 12 participants is sufficient for qualitative studies. However, for quantitative studies, a sample size of at least 30 participants is recommended to achieve sufficient statistical power.
Regarding the specific scenario you mentioned, a sample size of 20 students in the experimental group and 25 students in the control group may not be sufficient to detect small or moderate effects. It is recommended to use power analysis to determine the appropriate sample size for your study.
In terms of pilot studies, it is generally recommended to use a similar number of participants with similar characteristics in the pilot study as in the main study. This will ensure that the pilot study's results generalize to the larger sample in the main study.
Here are a few papers that discuss sample size consideration in quasi-experimental studies in education research:
Gliem, J. A., & Gliem, R. R. (2003). Calculating, interpreting, and reporting Cronbach's alpha reliability coefficient for Likert-type scales. Midwest research-to-practice conference in adult, continuing, and community education.
McQuarrie, E. F., Marzano, R. J., Pickering, D. J., & Pollock, J. E. (1996). A meta-analysis of intervention research with middle-school students. Journal of Educational Research, 89(4), 220–229.
Shadish, W. R., Cook, T. D., & Campbell, D. T. (2002). Experimental and quasi-experimental designs for generalized causal inference. Boston: Houghton, Mifflin and Co.
Dear researchers,
My research is an intervention study, a quasi-experiential RD, between-group design and non-randomized. This research includes both questionnaires and use of eye-tracking as an objective measure. The aim of the study is to evaluate the instructional efficiency/ implication of my intervention (Instructional design). is it ok if i consider the same or may be a bit more sample size similar to that of the previously conducted studies? or kind suggest how many samples will be required for this study.
Regards and thank you.
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