There are many types of resources that can be used to find Evidence Based information.
Strongest Types of Evidence:
Systematic Review: Usually focus on a clinical topic and answer a specific question. Searches the literature to find valid studies with good methodology (it is not original research, rather it looks at research that has already been conducted. Systematic review is conducted by systematically searching the literature with strategies outlined in the methods section of the paper. It might list the keywords and databases used. Might also refer to limits such as years searched, languages of publications, etc...
Meta Analysis: A systematic review which combines all of the research studies found as if it were one large study and then analyzes it with statistics.
Randomized Controlled Trials: Research study in which participants are randomly placed in a control and comparison group. Blinding of participants and researchers is an important aspect of reliable trials. Reduces bias.
Weaker Types of Evidence:
Cohort Studies: From a large population, follows patients who have a specific condition or receive a particular treatment over time and compared with another group that has not been affected by the condition or treatment studies. , (Example: Breast Cancer patient treated with a certain type of therapy and followed over time to determine if it is effective and compared to other breast cancer patients that did not receive this therapy and followed over time to see if there were any differences.) This is an observational study, so it is not as reliable as a Randomized Controlled Trial due to the fact that other factors can affect group.
Case Control Studies: Compare people who have the disease against those who do not have the disease (Example: Lung cancer studies looked back and found exposure to smoking.)
Case Series/Case Report: Treatment of individual patients or a report on a single patient (no control group for comparison). This is low evidence because it is only referring to one patient so not as reliable as other types of research. This may, however, be all that is available. (Example: First cases of AIDS were case reports of people experiencing symptoms, etc...)
Qualitative Studies:* Research that involves the collection of data in nonnumeric form, such as personal interviews, usually with the intention of describing a phenomenon.
Quantitative Studies:* Research that collects data in numeric form and emphasizes precise measurement of variables; often conducted in the form of rigorously controlled studies.
Quasi-experiments:* A type of experimental design that tests the effects of an intervention or treatment but lacks one or more characteristics of a true experiment (e.g. random assignment; a control or comparison group).
(*Melnyk, B. M., & Fineout-Overholt, E. (2005). Evidence-based practice in nursing & healthcare :A guide to best practice. Philadelphia: Lippincott Williams & Wilkins.)