Research Guides: Research Methods in Nursing: Types of Studies

Different study types shown in a Pyramid

Image provided courtesy of Chico State Meriam Library.

Case Reports

About Case Reports

Case reports (or studies) are lowest level of evidence in this grouping, but have value because they are also the first line of evidence and are where new issues and ideas emerge. This is why they form the base of our pyramid. A good case report will be clear about the importance of the observation being reported.

Case reports are articles that describe and interpret an individual case. They often describe:

Unique cases that cannot be explained by known diseases or syndromes
Cases that show an important variation of a disease or condition
Cases that show unexpected events that may yield new or useful information
Cases in which one patient has two or more unexpected diseases or disorders

If multiple case reports show something similar, the next step might be a case-control study to determine if there is a relationship between the relevant variables.

More Information from:Himmelfarb Library
Definition of Case Study from the Dictionary of Nursing Theory and Research.
Explanation of Case Study Method of Research from the Encyclopedia of Nursing Research.

Finding Case Reports in ASU Databases

CINAHL Complete This link opens in a new window
- This link opens in a new window
Full text access to journals, association publications, health care books, nursing dissertations, selected conference proceedings, evidence-based care sheets, diseases and conditions quick lessons, and continuing education modules.
Cochrane Library This link opens in a new window
Click on "Advanced Search" then select "Medical Terms (MeSH)" and type "Case Reports" (without quotes) in the search box.
MEDLINE This link opens in a new window
- This link opens in a new window
Option 1: Enter keywords for search then locate the Publication Type limiter and select “Case Reports”.
Option 2: Use the MeSH 2020 subject heading "Case Report".
APA PsycINFO This link opens in a new window
- This link opens in a new window
Use the Methodology limiter and select “Clinical Case Study” or use the subject “Case Report”.
PubMed Central This link opens in a new window
Enter keywords for search and click "Search". Then use the “Article Types” filter and select “Case Reports”.

Case Control Studies

About Case Control Studies

Case control studies are observational because no intervention is attempted and no attempt is made to alter the course of the disease. The goal is to retrospectively determine the exposure to the risk factor of interest from each of the two groups of individuals: cases and controls. These studies are designed to estimate odds.

A case control study compares patients who have a disease or outcome of interest (cases) with patients who do not have the disease or outcome (controls), and looks back retrospectively to compare how frequently the exposure to a risk factor is present in each group to determine the relationship between the risk factor and the disease.

They are also known as "retrospective studies" and "case-referent studies."

More Information from:Himmelfarb Library
Definition of Case Control Study from the Dictionary of Nursing Theory and Research.
Case Control Studies from the Oxford Textbook of Global Public Health.

Finding Case Control Studies in ASU Databases

Some Suggested Search Terms:

Case-Control Studies or Comparison Studies or Control Groups or Matched-Pair Analysis or Retrospective Studies

CINAHL Complete This link opens in a new window
- This link opens in a new window
Full text access to journals, association publications, health care books, nursing dissertations, selected conference proceedings, evidence-based care sheets, diseases and conditions quick lessons, and continuing education modules.
MEDLINE This link opens in a new window
- This link opens in a new window
Option 1: Enter keywords for search then in a separate search box enter: "case control study or case-control study"
Option 2: Use the MeSH 2020 subject heading "Case-Control Studies".
Then click on "Subject: Major Heading" in the left column, click "Show More" to locate subjects related to your research topic.
PubMed Central This link opens in a new window
Enter keywords for your research in the search box then click "Add".
In the drop-down menu for the second search line, select "MeSH Terms".
In the search box for the second search line enter: case control studies. Note: you can also try retrospective studies.
Click "Search".
APA PsycINFO This link opens in a new window
- This link opens in a new window
Option 1: Enter keywords for search then look for the "Methodology" box and select "--Retrospective Study".
Option 2: Enter keywords for search then in a separate search box enter: "case* control*" or "case comparison*" or case-comparison or "control group*)"not "Literature Review"

Cohort Studies

About Cohort Studies

Cohort design is "a study design where one or more samples (called cohorts) are followed prospectively and subsequent status evaluations with respect to a disease or outcome are conducted to determine which initial participants exposure characteristics (risk factors) are associated with it. As the study is conducted, outcome from participants in each cohort is measured and relationships with specific characteristics determined."

More Information from:Himmelfarb Library
Definition of Cohort from the Dictionary of Nursing Theory and Research.
Explanation of Cohort Design from the Encyclopedia of Nursing Research.
Cohort Studies from the Oxford Textbook of Global Public Health.

Finding Cohort Studies in ASU Databases

Some Suggested Search Terms:

Cohort Studies or Longitudinal Studies or Follow-up Studies or Prospective Studies or Retrospective Studies

CINAHL Complete This link opens in a new window
- This link opens in a new window
Full text access to journals, association publications, health care books, nursing dissertations, selected conference proceedings, evidence-based care sheets, diseases and conditions quick lessons, and continuing education modules.
MEDLINE This link opens in a new window
- This link opens in a new window
Option 1: Enter keywords for your search then in a separate search box enter: "cohort study" or "cohort study design" and click search.
Option 2: Use the MeSH 2020 subject heading "Cohort Studies".
Then click on "Subject: Major Heading" in the left column, click "Show More" to locate subjects related to your research topic.
PubMed Central This link opens in a new window
Click on the "Advanced Search" link then begin entering your keywords or PICO terms (Click "Add" after each term). Then use this wording: cohort or follow-up or longitudinal or prospective or retrospective
Then click "Add" and click "Search"
APA PsycINFO This link opens in a new window
- This link opens in a new window
Option 1: Enter keywords for search then look for the "Methodology" box and select one of the following: "Longitudinal Study", "Follow-up Study", "Prospective Study", or "Retrospective Study".
Option 2: Enter keywords for search then in a separate search box enter: "longitudinal study" or "follow-up study" or "prospective study" or "retrospective study".

Quasi-Experimental Studies

About Quasi-Experimental Studies

A quasi-experiment is an experiment in which the principal independent variable is manipulated by the researcher, and has some controls, but it lacks random assignment of individual subjects to the treatment conditions.

Definition of Quasi-experiment from the Dictionary of Nursing Theory and Research
Explanation of Quasi-experimental Research from the Encyclopedia of Nursing Research

Finding Quasi-Experimental Studies in ASU Databases

Some Suggested Search Terms:

before-after study or pre-post intervention study

CINAHL Complete This link opens in a new window
- This link opens in a new window
Full text access to journals, association publications, health care books, nursing dissertations, selected conference proceedings, evidence-based care sheets, diseases and conditions quick lessons, and continuing education modules.
MEDLINE This link opens in a new window
- This link opens in a new window
Option 1: Enter keywords for your search then in a separate search box enter: "quasi-experimental study" or "quasi-experimental study design" and click search.
Option 2: Use the MeSH 2020 subject heading "Non-Randomized Controlled Trials as Topic".
Then click on "Subject: Major Heading" in the left column, click "Show More" to locate subjects related to your research topic.

Randomized Controlled Trials

About Randomized Controlled Trials

Randomized Controlled Trials (RCT) are Clinical Trials that randomly assign participants into an experimental group or a control group. As the study is conducted, the only expected difference between the control and experimental groups is the outcome variable being studied.

More Information from:Himmelfarb Library
Definition of Randomized Controlled Trial from Taber's Cyclopedic Medical Dictionary
Definition of Clinical Trial from the Dictionary of Nursing Theory and Research>
Explanation of Clinical Trial from the Encyclopedia of Nursing Research

Finding Randomized Controlled Trials in ASU Databases

Cochrane Library This link opens in a new window
Open the "Advanced Search" page and begin entering your keywords. Use the Plus (+) sign to add additional lines as needed and select "All Text" in the drop-down menu.
When done add one more line. In the drop-down select "Publication Type" then type "Randomized Control Trial" in the search box.
Click "Run Search"
CINAHL Complete This link opens in a new window
- This link opens in a new window
Full text access to journals, association publications, health care books, nursing dissertations, selected conference proceedings, evidence-based care sheets, diseases and conditions quick lessons, and continuing education modules.
Clinical Trials.gov This link opens in a new window
Provided by the U.S. National Library of Medicine, this is a database of privately and publicly funded clinical studies conducted around the world. In addition to the studies, researchers can download content for analysis as well as view trends, charts, and maps.
MEDLINE This link opens in a new window
- This link opens in a new window
Option 1: To limit your results to randomized controlled trials, start a new search and enter your search terms.
Then scroll down and look for the Publication Type" category, then select the "Randomized Controlled Trials" option.
Option 2: Use the MeSH 2020 subject heading "Randomized Controlled Trial".
Then click on "Subject: Major Heading" in the left column, click "Show More" to locate subjects related to your research topic.
APA PsycINFO This link opens in a new window
- This link opens in a new window
In the initial search screen (or click on "New Search", enter your keywords for the search, then in a separate search box enter "Randomized Controlled Trial", and then look for the "Methodology" box and select one of the following: "Clinical Trial" or "Treatment Outcome".
PubMed Central This link opens in a new window
Click on the "Advanced Search" link then begin entering your keywords or PICO terms (Click "Add" after each term). Then use this wording: Randomized Control Trial
Then click "Add" and click "Search"

Systematic Reviews

About Systematic Reviews

A systematic review is a form of secondary research, guided by a detailed review protocol, that gathers primary studies and information from other sources on a clinical or policy question of interest and analyzes the data from these multiple studies to reach a conclusion. A systematic review involves the identification, selection, appraisal, and synthesis of the best available evidence for clinical decision making. A properly conducted systematic review uses transparent and reproducible strategies to reduce bias and instill rigor. It synthesizes information from both published and unpublished sources.

More Information from Encyclopedia of Nursing Research
Definition of Clinical Systematic Reviews from the Dictionary of Nursing Theory and Research
Explanation of Systematic Reviews from the Encyclopedia of Nursing Research

Finding Systematic Reviews in ASU Databases

Cochrane Library This link opens in a new window
Cochrane Library is an excellent database of evidence-based medicine and especially for its database of Systematic Reviews.
In your search results, make sure to select the "Review" option located under the "Cochrane Reviews" limit at the left.
CINAHL Complete This link opens in a new window
- This link opens in a new window
Full text access to journals, association publications, health care books, nursing dissertations, selected conference proceedings, evidence-based care sheets, diseases and conditions quick lessons, and continuing education modules.
MEDLINE This link opens in a new window
- This link opens in a new window
To limit your results to systematic reviews, start in the "Advanced Search" screen, scroll down and ook for the Publication Type" category, then select the "Systematic Review" option.
PubMed Central This link opens in a new window
To limit your results to systematic reviews, conduct a search then look for the "Article Type" limiter in the left column, then select "Systematic Reviews".
APA PsycINFO This link opens in a new window
- This link opens in a new window
Option 1: Enter keywords for search then look for the "Methodology" box and select "Systematic Review".
Option 2: Enter keywords for search then in a separate search box enter: "Systematic Review".

Free Web-Based Databases

PEDro
PEDro is a free database of over 46,000 randomised trials, systematic reviews and clinical practice guidelines in physiotherapy.
Conduct an advanced search and select "systematic review" in the "Method" drop-down menu.
speechBITE
Database of evidence-based intervention studies across the scope of speech pathology practice.
Conduct an advanced search and select "Systematic Review" in the "Research Design" drop-down menu.

Meta-Analyses

About Meta-Analyses

A subset of systematic reviews; a method for systematically combining pertinent qualitative and quantitative study data from several selected studies to develop a single conclusion that has greater statistical power. This conclusion is statistically stronger than the analysis of any single study, due to increased numbers of subjects, greater diversity among subjects, or accumulated effects and results.

More Information from: Himmelfarb Library
Definition of Meta-Analysis from the Dictionary of Nursing Theory and Research
Explanation of Meta-Analysis from the Encyclopedia of Nursing Research

Finding Meta-Analyses in ASU Databases

Cochrane Library This link opens in a new window
Open the "Advanced Search" page and begin entering your keywords. Use the Plus (+) sign to add additional lines as needed and select "All Text" in the drop-down menu.
When done add one more line. In the drop-down select "Publication Type" then type "meta analysil" in the search box.
Click "Run Search"
CINAHL Complete This link opens in a new window
- This link opens in a new window
Full text access to journals, association publications, health care books, nursing dissertations, selected conference proceedings, evidence-based care sheets, diseases and conditions quick lessons, and continuing education modules.
MEDLINE This link opens in a new window
- This link opens in a new window
Option 1: To limit your results to meta-analyses, start a new search and enter your search terms.
Then scroll down and look for the Publication Type" category, then select the "Meta-Analysis" option.
Option 2: Use the MeSH 2020 subject heading "Meta-Analysis".
Then click on "Subject: Major Heading" in the left column, click "Show More" to locate subjects related to your research topic.
PubMed Central This link opens in a new window
To limit your results to Meta-Analysis, conduct a search then look for the "Article Type" limiter in the left column, then select "Meta-Analysis".
APA PsycINFO This link opens in a new window
- This link opens in a new window
Option 1: Enter keywords for search then look for the "Methodology" box and select "Meta Analysis".
Option 2: Enter keywords for search then in a separate search box enter: "Meta Analysis".

Ask a Librarian

Need research assistance? One-on-one help is available via the Library’s Virtual Reference Room in Blackboard or phone (325-486-6534) during the following hours:

Monday-Thursday: 9 a.m. – 7 p.m.
Friday: 9 a.m. – 5 p.m.
Saturday: 2 – 6 p.m.
Sunday: 1 – 5 p.m.

You can also contact us via

email or by posting on the Ask a Librarian Discussion Board in Blackboard.
Messages sent outside of normal service hours will be answered the next day the library is open (check Library Hours of Operation for current schedule).