An empirical or primary research article reports on a study conducted by the authors. A review of the literature is an important step in any research study, but an empirical article goes on to describe the details of a specific study. This type of article:

• Asks a research question or states a hypothesis
• Identifies the population and specifies the number of subjects studied (sample size) and how they were selected (sampling method)
• Describes the source of the data and methods used to collect it
• Describes the research design or method (though it is not always explicitly stated)
• Includes a results section describing major findings

Words to look for as clues include: analysis, study, investigation, examination, experiment, numbers of people or objects analyzed, control group, or survey.

To contrast, the following are NOT primary research articles (they are secondary sources):

• Literature reviews*
• Meta-Analyses/Review articles* (arrive at conclusions based on research from many other studies)
• Editorials
• Letters
• Chapters in books
• Encyclopedia articles
• Speeches and interviews

* Literature reviews and meta-analyses also describe the authors' research method/methodology, focusing on their database search strategy and development of criteria for including or excluding individual study results. These articles are still secondary sources because they synthesize the findings of multiple research studies; the authors are not the primary researchers.

As you read and evaluate articles, look at the methods or methodology to determine the type of research conducted:

• Randomized controlled trials (RCTs)
• Cohort studies
• Case-control studies
• Cross-sectional studies
• Qualitative studies
• Other types and definitions of study designs 

Research study types are not always obvious. Researchers may use elements of more than one design to achieve their purpose. Read carefully and use your best judgement to identify the overall category or type of a particular study's methodology.