In order to select the best database for your particular question you need to know…
Filtered resources appraise the quality of studies and often make recommendations for practice.
Evidence is not always available via filtered resources. Searching the primary literature may be required. It is possible to use specific search strategies in MEDLINE and other databases to achieve the highest possible level of evidence.
Evidence in these resources may vary from expert opinion to high levels of evidence. They can inform you about your research topic and answer your background question.
The TRIP Database is a clinical search engine designed to allow users to quickly and easily find and use high-quality research evidence to support their practice and/or care.
The search process...
Review the Foley Library's Searching Health Science Literature tutorial to help you learn more on searching.
Review the Centre for Evidence-Based Medicine "Finding the evidence: a how-to guide".