Research, with its’,all ethical dimensions, is trusteeship with the researcher to explore, reveal and disseminate facts to bounce it to the owner. To do this, introducing the right and reliable source of research data (Statistical population) is the prim discipline to consider although unfortunately this initial regulation is considered less in many researches. Therefore, invalid and unreliable source of date is bothering abundant researches to invalidate their findings regarding facts investigation. Vague research population, sample size, sample selection, and even sample assignment procedure were the most predominant insufficiency biasing research to unveil facts in over 1500 research articles, considerable number of research reports, graduate theses and even Ph.d. dissertations that reviewed in this analytical documentary investigation article. Providing accurate and adequate research proposal,proper and right data,sufficient statistical procedures, realistic analysis, deduction and generalization are four fundamental research principles stressed and enlightened in this article to assist researchers to avoid research obstacles. Because, the more blemished these research principles, the more inaccurate data, and hence the more unreliable results. Thus, recent precise and applicable on-line calculation procedures to determine the sample size based on the characteristics of the confidence level, confidence interval, size, and mos t importantly, the effect size of the research population introduced in this article.