To locate empirical research in ERIC (ProQuest):
Empirical research is research that uses observation or experiments to answer a question or test a hypothesis. For example, a research question might ask, "Does a specific educational intervention work with a specific age group or in a specific type of setting or for a specific subject? The results are based upon actual evidence as opposed to theory or conjecture. The results should be able to be replicated in follow-up studies. Empirical research articles are published in peer-reviewed journals.
Peer-review: Scholarly peer review (which is also known as refereeing) is the process when authors submit their scholarly work (articles, conference papers, ideas, research) to the scrutiny of peers in their field who are experts in that field. The Ulrichs Periodical Directory database can be used to see if a journal is identified as a peer-reviewed publication. It should be noted that Ulrichs does not judge the relative merits of specific publications and the peer-review process. Instead, journals are identified as peer-reviewed based on the journal publisher's self-reported designation.
Primary sources refer to information collected firsthand from such sources as historical documents, literary texts, artistic works, experiments, surveys, and interviews. Thus, articles where the author is describing their own experiments would be considered a primary source. In science and the social sciences, research articles are considered primary sources. In history, a much wider range of sources would also be included everything from original research and original works of fiction to items created during the period that is being studied. These can include personal papers including diaries, journals, and correspondence; legal notices and records for births, deaths, divorces, marriages, and military; photographs, and jewelry.
Secondary sources refer to another person's second-hand account of something such as in a literature review. Thus, an experiment that is described by someone other than the researcher(s) would be considered a secondary source. Accounts found in newspapers, radio, and television about research findings would be considered secondary sources.
APA has specific rules for citing a primary source that is cited using a secondary source.
It is always best to read the original or primary sources, but sometimes this is difficult if the original work was published in another language or was published in a book that is difficult to obtain. In such a case, you would need to cite the original or primary source in the text of the paper, but you would provide a reference in the reference list for the secondary source.
a. Within the Text
According to Skinner (as cited in Freud, 1923), Freud took the position ….
b. In the Reference List
Skinner, B. F. (1974). About behavioralism. New York, NY: Knopf.
See also the APA Style website's FAQ on how to format a secondary source.