Completing a research project is a lot like taking a road trip. There are several factors to consider beyond your research question, including what type of research method to use, data collection type, and more. While our roadmap focuses on a lot of steps, we can use this and eliminate steps that do not apply to your project. Even though our result may be a paper or presentation for class, you can use this to guide in your practical experience, poster, or maybe even a conference presentation!
Image is from the Cochrane Library Cochrane Essentials Module 2
“Evidence Pyramid” by Tufts University can be reused under the BY-NC-SA license 4.0
| Levels of Evidence |
Qualifying Studies |
| I | High Quality, multicenter or single-center; randomized controlled trial with adequate power; or systematic review of these studies |
| II |
Lesser quality, randomized controlled trial; prospective cohort study; or systematic review of these studies |
| III | Retrospective comparative controlled trial; prospective cohort study; or systematic review of these studies |
| IV | Case-Series |
| V | Expert opinion; case report or clinical example; or evidence based on physiology, bench research, or "first principles" |
Levels of Evidence Based Medicine Chart: Chung KC, Swanson JA, Schmitz D, et al. Introducing evidence-based medicine to plastic and reconstructive surgery. Plast. Reconstr. Surg. 2009;123:1385–1389.
An examination and and evaluation of someone else's work. It's part of the evidence synthesis process where the writer(s) bring together evidences and sources to make inform the reader on a specific topic.
| Evidence-Based Medicine Practice Guidelines |
Treatment, therapy, intervention, drug, practices, etc. recommendations that are supported by standards of evidence. Model for how providers provide care for patients. These are considered "best practices." |
| Systematic Reviews |
Focus on a clinical topic of answer a specific question. Essentially an extensive literature that identifies studies by following a specific methodology. Needs at least two people to complete as well as a protocol and systematic search strategy. Studies are reviewed, assessed for quality and results summarized.
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| Meta-Analysis |
Similar to Systematic Reviews. These examine a number of studies on a specific topic and combine results using an accepted statistical method to report the results as if it were one study. Considered the highest levels of evidence-based research.
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Non-research information includes materials that meet methodological requirements for research studies. They can involve critical analysis and used to demonstrate evidence. However, these articles tend to be "upstream" or secondary sources. They do not include original research. The chart below includes a description of these types of materials.
| Non-Evidence Based Expert Opinion | Statements, speeches, and editorials written by prominent members of a field that are based on conjecture, observation, and belief. |
| Non-Evidence Based Practice Guidelines | Guidelines in place because of authority, providence, or alternative approaches to healthcare. |
| News Articles | Summaries of research or medical opinions written by journalists for the public. |
| Editorials | Opinions by experts and non-experts written in newspapers, magazines, or academic journals. |
| Commentaries |
Identified by informal and non-reviewed short article pertaining to particular concept or idea. Similar to editorials. |
These are common in Health Sciences. Review articles are generally overviews of literature found on topics but do not meet the methodological requirements for a Systematic Review. They are a type of evidence synthesis that involves some critical analysis. They can demonstrate evidence but are secondary articles and not original research.
Observational studies are self explanatory. The researcher observes the effect of risk factor, test, treatment, intervention, without interfering with the participant. The researcher simply observes, without interfering, effecting the results.
| Cohort Studies | One or more samples are followed for a period of a time and result in status evaluations over a period of time or at the end of a study, with respect to a disease or outcome. The study is conducted to determine which initial participants risk factors (or exposure characteristics) are associated with it. The outcome of the participants in each cohort is measured and relationships with specific characteristics determined. |
| Case Control Studies |
Compares patients who have a disease (cases) or expected outcome to those who do not have the disease or expected outcome (controls). It looks back to compare who frequently the exposure to risk factors are present in each group to determine the relationship between the risk factor and the disease. Since these are observational, no intervention or attempt is made to alter the course of the disease. Studies are designed to estimate odds. |
| Individual Case Reports | An article that describes and interprets and individual case. Written with great detail. Typically cover unique cases that cannot be explained by known diseases or syndromes; often focus on rare diseases. Can help identify new trends or disease |
In this type of study the researcher introduces an intervention and studies the effects. There is also a control group for the researcher to observe changes over time.
| Randomized Control Trials (RCT) |
Carefully planned experiments. They introduce a treatment or exposure and the research studies its effect on study participants. Include methodologies that reduce potential for bias through randomization and blinding that allow for comparison between intervention groups and control (no intervention) groups. A RCT can provide evidence of cause and effect. There are several types of randomization and blinding. |
| Non-Randomized Control Trials |
Experiments centering on a new therapy, treatment, drug, etc. in a clinical environment with an experimental group and a control group. Researchers and participants know what type of intervention participants are receiving. They are detailed; describing the background, methods, procedures, results, etc. |
