Clues that the article is a primary source:
- Analyzes the data collected by the authors.
- Often extremely narrow in scope.
- Abstract may include phrases like "we observed," "sampling was conducted," etc.
- Usually includes a methods section.
- Will include a review of past work by others, but this is meant to provide context for original data collection and analysis.
The article below is a primary source because the authors collected the data themselves.
Clues that the article is a secondary source:
- Describes the work of other scientists.
- Surveys the state of research within a narrow field of study.
- Title or abstract includes the terms review, literature review, or meta-analysis.
- May not include a methods section.
The article below is a secondary source, not only because it says "review" in the title, but also because the article mentions it is a survey of other articles.