Primary, Secondary, and Tertiary Literature
Empirical Study?
A professor may also mention the term "empirical" to students. In many cases, the term empirical is used to mean the exact same thing as a "primary" or "research." However, specifically, an empirical study is one that reports research based on direct observations or experiments. It often seeks to answer a specific question or to test a hypothesis.
The research may use quantitative research methods, generating numerical data which attempts to establish causal relationships between two or more variables. But empirical research articles may also use qualitative research methodology, in which the author objectively and critically analyzes beliefs or behaviors (etc.) without the analysis of clearcut numerical data.
Peer Review
Before a research paper is accepted for publication in the scientific literature, it is subjected to the "peer review" process.
This means that the publisher sends a copy of the submitted paper to one or more scientists working in the same field. These peer scientists read the paper and assess the quality of the research and the paper describing it.
They look at such factors as whether or not the design of the experiment was appropriate for the hypothesis being tested, whether sufficient data were collected, and whether the conclusions follow logically from the results of the experiment.
They also consider whether the overall topic was of sufficient importance and interest to warrant publication.