Different study designs present higher level evidence depending on the type of clinical question to be answered.
A report on a series of patients with an outcome of interest. No control group is involved.
Case-control studies begin with the outcomes and do not follow people over time. Researchers choose people with a particular result (the cases) and interview the groups or check their records to ascertain what different experiences they had. They compare the odds of having an experience with the outcome to the odds of having an experience without the outcome.
The observation of a defined population at a single point in time or time interval. Exposure and outcome are determined simultaneously.
Cohort Study (Prospective Observational Study)
A clinical research study in which people who presently have a certain condition or receive a particular treatment are followed over time and compared with another group of people who are not affected by the condition.
Controlled Clinical Trial
A type of clinical trial comparing the effectiveness of one medication or treatment with the effectiveness of another medication or treatment. In many controlled trials, the other treatment is a placebo (inactive substance) and is considered the "control."
Randomized Controlled Trial
A controlled clinical trial that randomly (by chance) assigns participants to two or more groups. There are various methods to randomize study participants to their groups.
A summary of the clinical literature. A systematic review is a critical assessment and evaluation of all research studies that address a particular clinical issue. The researchers use an organized method of locating, assembling, and evaluating a body of literature on a particular topic using a set of specific criteria. A systematic review typically includes a description of the findings of the collection of research studies. The systematic review may also include a quantitative pooling of data, called a meta-analysis.
A way of combining data from many different research studies. A meta-analysis is a statistical process that combines the findings from individual studies.
Adapted from Study Designs. (2007, November 3.) In NICHSR Introduction to Health Services Research: a Self-Study Course. Retrieved June 23, 2009 from http://www.nlm.nih.gov/nichsr/ihcm/06studies/studies03.html
Glossary of EBM Terms. June 23, 2009 from http://www.cebm.utoronto.ca/glossary/index.htm#top
Medical, health, and scientific research is based on unique data collection and structuring.
The Johns Hopkins School of Nursing Levels of Evidence are as follows:
Experimental study, randomized controlled trial (RCT)
Systematic review of RCTs, with or without meta-analysis
Systematic review of a combination of RCTs and quasi-experimental, or quasi-experimental studies only, with or without meta-analysis.
Systematic review of a combination of RCTs, quasi-experimental and non-experimental, or non-experimental studies only, with or without meta-analysis.
Qualitative study or systematic review, with or without meta-analysis
Opinion of respected authorities and/or nationally recognized expert committees/consensus panels based on scientific evidence.
Clinical practice guidelines
Based on experiential and non-research evidence.
Link to Johns Hopkins Nursing Evidence Based Practice in the LCC Library. (ebook)
Dang, D., & Dearholt, S.L. (2018). Johns Hopkins nursing evidence-based practice : Model & guidelines (3rd ed). Sigma Theta Tau International.
There are several ways to determine if an article qualifies as quantitative or qualitative. First, read the abstract. Often there is an explicit mention of methodology that is one or the other, or both. Next, think about the kinds of research methods that are quantitative or qualitative from the rubric of characteristics below. And finally, remember that most qualitative research results in some kind of measurable (or quantitative) data. Because an evidence-based nursing practice relies on objective evidence, measurable data is the standard—even subjective data gathered from qualitative methods will be collated or measured.
If your assignment requires that you find quantitative or qualitative support for your research, build your search using terms that indicate one or the other. For example:
midwif* AND postpartum qualitative (results will include the word qualitative somewhere)
midwif* AND postpartum interviews (results tend toward qualitative research)
midwif* AND postpartum quantitative (results will include the word quantitative somewhere)
midwif* AND postpartum statistics (results tend toward quantitative research)
Characteristics of quantitative and qualitative research include:
This video demonstrates how to determine if an article is a quantitative study or not.
Is there an author of the document? Can you determine their credentials? If you cannot determine the author of the site, then think twice about using it as a resource.
Is the site sponsored by a group or organization? If it is, does the group advocate a certain philosophy? Try to find and read "About Us" or similar information.
Is there any bias evident in the site? Is the site trying to sell you a product? Ask why the page was put on the web?
Is there a date on the website? Is it sufficiently up-to-date? If there is no date, think twice about using it. Undated factual or statistical information should never be used.
How credible and authentic are the links to other resources? Are the links evaluated or annotated in any way?
Evaluating information and successful nursing practice is based on:
"Maintaining a healthy skepticism about the quality and validity of all information." (AAMC)
"Making decisions based on evidence, when such is available, rather than opinion." (AAMC)
Many scholarly research articles include statistical analysis of numerical data gathered during a study or experiment. To understand these results, check out these explanations.
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