Sources of information are often categorized as primary or secondary depending upon their originality.
A primary source provides direct or firsthand evidence about an event, object, person, or work of art. Primary sources provide the original materials on which other research is based and enable students and other researchers to get as close as possible to what actually happened during a particular event or time period. Published materials can be viewed as primary resources if they come from the time period that is being discussed, and were written or produced by someone with firsthand experience of the event. Often primary sources reflect the individual viewpoint of a participant or observer. Primary sources can be written or non-written (sound, pictures, artifacts, etc.). In scientific research, primary sources present original thinking, report on discoveries, or share new information.
Examples of primary sources:
- Autobiographies and memoirs
- Diaries, personal letters, and correspondence
- Interviews, surveys, and fieldwork
- Internet communications on email, blogs, listservs, and newsgroups
- Photographs, drawings, and posters
- Works of art and literature
- Books, magazine and newspaper articles and ads published at the time
- Public opinion polls
- Speeches and oral histories
- Original documents (birth certificates, property deeds, trial transcripts)
- Research data, such as census statistics
- Official and unofficial records of organizations and government agencies
- Artifacts of all kinds, such as tools, coins, clothing, furniture, etc.
- Audio recordings, DVDs, and videorecordings
- Government documents (reports, bills, proclamations, hearings, etc.)
- Technical reports
- Scientific journal articles reporting experimental research results
Secondary sources describe, discuss, interpret, comment upon, analyze, evaluate, summarize, and process primary sources. A secondary source is generally one or more steps removed from the event or time period and are written or produced after the fact with the benefit of hindsight. Secondary sources often lack the freshness and immediacy of the original material. On occasion, secondary sources will collect, organize, and repackage primary source information to increase usability and speed of delivery, such as an online encyclopedia. Like primary sources, secondary materials can be written or non-written (sound, pictures, movies, etc.).
Examples of secondary sources:
- Biographical works
- Reference books, including dictionaries, encyclopedias, and atlases
- Articles from magazines, journals, and newspapers after the event
- Literature reviews and review articles (e.g., movie reviews, book reviews)
- History books and other popular or scholarly books
- Works of criticism and interpretation
- Commentaries and treatises
- Indexes and abstracts