Which of the following is an example of a primary source in research?

The identification of an original research article as a primary source is rooted in its role in the research process. Primary sources are direct, firsthand pieces of evidence or data that provide original insights or findings. They typically involve new research conducted by the authors, including methodologies, results, and conclusions drawn from the data collected.

In this context, an original research article presents original research rather than summarizing or analyzing existing literature. It offers unique experimental or observational data that contribute new knowledge to the field. By reporting on the authors' own research findings, these articles serve as foundational pieces in scientific literature, allowing others to build upon this original work or examine the findings directly.

In contrast, a review article analyzes and synthesizes information from multiple studies, thus serving as a secondary source. A textbook, too, summarizes concepts from primary research and is another form of secondary literature. A standard operating procedure document, while important for outlining processes, does not convey novel research findings or original data and therefore does not qualify as a primary source.