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Research Process

These pages offer an introduction to the research process at a very general level.

Evidence Pyramid

Systematic reviews and meta-analyses are situated at the top of what is known as the “Evidence Pyramid” (see figure below). As you move up the pyramid the amount of available literature on a given topic decreases, but the relevancy and quality of that literature increases. Systematic reviews and meta-analyses are considered to be the highest quality evidence on a research topic because their study design reduces bias and produces more reliable findings. However, you may not always be able to find (or need to find) the highest level of evidence to answer your research question. In the absence of the best evidence, you then need to consider moving down the pyramid.

Image of the Evidence Pyramid for research.

EBM Pyramid and EBM Page Generator, copyright 2006 Trustees of Dartmouth College and Yale University. All Rights Reserved.
Produced by Jan Glover, David Izzo, Karen Odato and Lei Wang.

Systematic Reviews

A systematic review is a high-level overview of primary research on a particular research question that systematically identifies, selects, evaluates, and synthesizes all high quality research evidence relevant to that question in order to answer it. In other words, it provides an exhaustive summary of scholarly literature related to a particular research topic or question. A systematic review is often written by a panel of experts after reviewing all the information from both published and unpublished studies. The comprehensive nature of a systematic review distinguishes it from traditional literature reviews which typically examine a much smaller set of research evidence and present it from a single author’s perspective. Systematic reviews originated in the biomedical field and currently form the basis of decision-making in Evidence-Based Treatment (EBT) and evidence-based behavioral practice (EBBP).  

For additional information, read this entry in the e-reference book The A-Z of Social Research:


Systematic reviews often use statistical techniques to combine data from the examined individual research studies, and use the pooled data to come to new statistical conclusions. This is called meta-analysis, and it represents a specialized subset of systematic reviews. Not all systematic reviews include meta-analysis, but all meta-analyses are found in systematic reviews. Simply put, a systematic review refers to the entire process of selecting, evaluating, and synthesizing all available evidence, while the term meta-analysis refers to the statistical approach to combining the data derived from a systematic-review. Conclusions produced by meta-analysis are statistically stronger than the analysis of any single study, due to increased numbers of subjects, greater diversity among subjects, or accumulated effects and results. Meta-analyses have become common in the social and biomedical sciences. However, some challenge the validity of meta-analysis, arguing that combining data from disparate studies produces misleading or unreliable results.

For additional information, read this entry in e-reference book The Concise Corsini Encyclopedia of Psychology and Behavioral Science:

Finding Systematic Reviews & Meta-Analyses

Since there are far fewer systematic reviews and meta-analyses than most other types of research, you will often need to broaden your search terms when searching in the Library’s Databases or the Internet. Also, keep in mind that the term "systematic review" originated in the medical field, so you can expect to see the majority of articles related to medical areas and conditions.

Locating systematic reviews and meta-analyses is extremely beneficial not only because they provide high-quality evidence, but also because they will include extensive references to primary studies relevant to your research topic.

See the Resources box below for instructions on locating systematic reviews and meta-analyses in the Library databases.

Systematic Reviews & Meta-Analyses Workshop

This workshop provides an introduction to library resources which can be used to locate systematic reviews and meta-analysis studies.


APA PsycInfo
Compiled by the American Psychological Association (APA), APA PsycInfo covers all aspects of psychology, plus the behavioral aspect of education, medicine, sociology, law, management, and other fields. To limit your APA PsycInfo search results to systematic reviews, select “Systematic Review” within the Methodology box (as shown below) and then type your search terms into the search box.

Screenshot of the MEDLINE Advanced Search limiter for Methodology with Systematic Review selected.

CINAHL with Full Text
CINAHL allows you to limit your publication type not only systematic reviews or meta analyses, but also to a "meta synthesis." This publication type value is applied to articles that indicate the presence of a qualitative methodology that integrates results from a number of different, but inter-related studies. To limit your results, select “Systematic Reviews” (or Meta Analysis or Meta Synthesis) within the Publication Type box (as shown below) and then type your search terms into the search box.

Screenshot of the CINAHL Advanced Search limiter for Publication Type with Meta Analysis selected.

Alternatively, you may wish to limit your CINAHL search results to Evidence-Based Practice, as shown below. Applying this limiter allows you to limit results to: articles from evidence-based practice journals; articles about evidence-based practice; research articles (including systematic reviews, clinical trials, meta analyses, etc.) and commentaries on research studies (applying practice to research). Selecting Evidence-Based Practice will produce a broader set of results than applying a single publication type limiter.

Screenshot of the CINAHL Advanced Search limiter for Evidence-Based Practice selected.

Cochrane Library
Cochrane Library is a collection of six databases that contain different types of high-quality, independent evidence to inform healthcare decision-making, and a seventh database that provides information about Cochrane groups. To access Cochrane Library, go to the Library home page and select A-Z Databases.

Select Advanced Search and then click on Search limits to choose your Cochrane Reviews as shown below.

Screenshot of the Cochrane Reviews Advanced Search Limits with Cochrane Reviews highlighted.

MEDLINE with Full Text
MEDLINE provides authoritative medical information on medicine, nursing, dentistry, veterinary medicine, the health care system, pre-clinical sciences, and much more. To limit your results to systematic reviews, select “Systematic Reviews” within the Subject Subset box (as shown below) and then type your search terms into the search box.

Screenshot of the MEDLINE Advanced Search limiter for Subject Subset with Systematic Reviews selected.

OVID Nursing Full Text
To access OVID, go to the Library home page and select A-Z Databases. On the OVID Basic Search screen, select from among the options under the field EBM-Evidence Based Medicine, as shown below. To select both Meta Analysis and Systematic Review, hold down the Control button on your keyboard.

Screenshot of the OVID search screen with Meta Analysis and Systematic Review selected.

PubMed systematic reviews cover a broad set of articles that build consensus on biomedical topics and medical genetics. PubMed also includes meta-analyses, reviews of clinical trials, evidence-based medicine, consensus development conferences, and guidelines. After doing your search, click on the “Article types” limit at the top of the left-hand column and select “Systematic Reviews.”

Note that this Systematic Reviews filter in PubMed will include meta-analyses results. If however, you want to search for only for meta-analyses, select the Meta-Analysis filter under Article Types. You will need to deselect everything in this filter except meta-analyses. Alternatively, you can also search for systematic reviews in PubMed by clicking on the Clinical Queries link on PubMed’s home page.

Roadrunner Search
Roadrunner is a great starting point for your research as it searches approximately 95% of the library’s database content, including articles, e-books and videos. To include systematic reviews in your Roadrunner search results, include the phrase “systematic review” in one of the search boxes and change the drop-down menu to TI Title (as shown below).

Screenshot of the Roadrunner Advanced Search with an example search for "systematic review."

Web of Knowledge
Web of Knowledge provides access to current and retrospective bibliographic information, author abstracts, and cited references in social science journals that cover more than 50 disciplines. Note there is no full-text within this database. To include systematic reviews in your Web of Knowledge search results, enter your topic keyword on the top line for Topic. On the second line, type “systematic review” and change the drop-down box to Title (as shown below).

Biondi-Zoccai, G., Lotrionte, M., Landoni, G., & Modena, M. (2011). The rough guide to systematic reviews and meta-analyses. HSR Proceedings in Intensive Care & Cardiovascular Anesthesia, 3(3), 161-173.

Borenstein, M., Hedges, L. V., Higgins, J., & Rothstein, H. R. (2009). Introduction to meta-analysis. Hoboken, NJ: John Wiley & Sons.

Davis, J., Li, C., & Leucht, S. (2009). Meta-analysis. In R. Mullner (Ed.), Encyclopedia of health services research. (pp. 765-769). Thousand Oaks, CA: SAGE Publications, Inc.

Egger, M., Smith, G. D., & Altman, D. G. (Eds.). (2008). Systematic reviews in health care: Meta-analysis in context. Chichester, GBR: BMJ Publishing Group.

Garg, A., Hackam, D., & Tonelli, M. (2008). Systematic review and meta-analysis: when one study is just not enough. Clinical Journal Of The American Society Of Nephrology: CJASN, 3(1), 253-260.

Glasziou, P., Irwig, L., Bain, C., & Colditz, G. (2001). Systematic reviews in health care: A practical guide. Port Chester, NY: Cambridge University Press.

Gough, D., Oliver, S., & Thomas, J. (2012). Introducing systematic reviews. In D. Gough, S. Oliver & J. Thomas (Eds.), An Introduction to Systematic Reviews (pp. 1-16). Los Angeles, CA: SAGE Publications, Inc.

Hernandez, A. (2009). Meta-analysis and literature review. In M. Kattan (Ed.), Encyclopedia of medical decision making. (pp. 763-768). Thousand Oaks, CA: SAGE Publications, Inc.

Neely, J., Magit, A. E., Rich, J. T., Voelker, C. J., Wang, E. W., Paniello, R. C., & ... Bradley, J. P. (2010). A practical guide to understanding systematic reviews and meta-analyses. Otolaryngology-Head & Neck Surgery, 142(1), 6. doi:10.1016/j.otohns.2009.09.005

Rudnicka, A., & Owen, C. (2012). An introduction to systematic reviews and meta-analyses in health care. Ophthalmic & Physiological Optics, 32(3), 174-183. doi:10.1111/j.1475-1313.2012.00901.x

Sharland, E. (2012). Systematic review. In M. Gray, J. Midgley, & S. Webb (Eds.), The SAGE handbook of social work. (pp. 482-499). London, United Kingdom: SAGE Publications, Inc.

Sirin, S. (2010). Meta-analysis. In N. Salkind (Ed.), Encyclopedia of research design. (pp. 794-799). Thousand Oaks, CA: SAGE Publications, Inc.

Uman, L. (2011). Systematic reviews and meta-analyses. Journal of the Canadian Academy of Child and Adolescent Psychiatry, 20(1), 57-59.

Webb, C., & Roe, B. H. (Eds.). (2008). Reviewing research evidence for nursing practice: Systematic reviews. Malden, MA: Blackwell.

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