Levels of evidence in research

What levels of evidence are present in relation to research and practice, and why it is important regardless of the method you use? In regards to Evidence based practice in medicine/critical care for a Nurse practitioner. APA format, 250 words

The recent healthcare system has been the subject of transformations it terms of its design, practices and construction with the aim of further improving healthcare provision. There has been an emerging trend in evidence-based practice which basically requires decisions being made after considering and evaluating information from various sources. Physicians of the modern world make decisions based on a variety of clients’ and medical information emanating from project evaluations and credible research (Hamilton, 2003)…………………………..words 323