What is the suggested minimal sample size for Ex Post Facto and experimental research?

The suggested minimal sample size for Ex Post Facto and experimental research is important because having an adequately powered sample allows for more reliable and valid results. While a sample size of 15 may seem low, it can provide sufficient statistical power for detecting effects in certain types of studies, especially if the effects are large or if the research is preliminary in nature.

In Ex Post Facto research, where the researcher looks back in time to investigate relationships or outcomes based on already existing differences, a smaller sample size might suffice under specific circumstances, particularly if the research is focused or if other analytical methods are employed that cater to smaller samples.

However, it’s worth noting that larger samples, such as 30, 50, or 100, can enhance the robustness of the research findings by reducing the potential for Type I and Type II errors. Selecting a small sample does come with limitations in terms of the generalizability of findings; yet, a size of 15 can sometimes still provide meaningful insights, particularly in exploratory studies or pilot research aiming to generate hypotheses for further investigation. Thus, the choice of 15 reflects a balance between feasibility and the need for initial data collection in specific research contexts.

This answer is informed by the nuances of research design