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Research Skills Tutorial

Primary, Secondary and Tertiary Information Sources

What does primary vs. secondary vs. tertiary mean? 

The distinction between primary, secondary and tertiary sources hinges on how far from the original event or phenomenon the information source is created. Is it first-hand knowledge? A second-hand interpretation? A third-hand synthesis and summary of what is known? 

  • Primary sources are created as close to the original event or phenomenon as it is possible to be. For example, a photograph or video of an event is a primary source. Data from an experiment is a primary source. 
  • Secondary sources are one step removed from that. Secondary sources are based on or about the primary sources. For example, articles and books in which authors interpret data from another research team's experiment is a secondary source. 
  • Tertiary sources are one further step removed from that. Tertiary sources summarize or synthesize the research in secondary sources. For example, textbooks and reference books are tertiary sources.

Why is this important? Because different kinds of research call for using primary, secondary, and tertiary sources in different ways. For example, a research paper usually requires a combination of primary and secondary sources.

Examples of Primary Sources

Topic: Performance of a Company 

Example of an Appropriate Primary Source: Annual Reports; SEC Filings

Topic: Sinking of a ship in 1920

Example of an Appropriate Primary Source: Newspapers and newsreels about the event; a diary

Topic: Effect of a new medicine on a virus

Example of an Appropriate Primary Source: Data from an experiment 

Where To Find Primary Sources

In the sciences, peer-reviewed research articles are considered primary sources because they are full of direct evidence in the form of data. Try searching a science database for articles containing original research and experiments. 

Newspapers are key primary sources for past current events. Try searching newspaper databases.

Museums, archives, historical societies, libraries with special collections, and cultural institutions collect pictures, letters, diaries, archival materials, ephemera, etc. Many collections are now available online. Try searching:

If you need statistics and datasets, try:

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