Elements of an Ethical Sampling Plan

Read the Suhonen, R., Stolt, M., Katajisto, J., & Leino-Kilpi, H. (PDF) (I WILL UPLOAD THE ARTICLE.) article. Based on this article and what you find in your EBP text, what would you consider to be the elements of an ethical sampling plan? Would it be possible to create a sampling plan that is equitable for all patients?