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Library & Research Know-How

LARK: An Open Educational Resource


Categorizing Sources

Once you have your research question, you’ll need information sources to answer it and meet the other information needs of your research project. You’ll usually have a lot of sources available to meet the information needs of your projects. In today’s complex information landscape, just about anything that contains information can be considered a potential source. Here are a few examples:

  • Books and encyclopedias
  • Websites, web pages, and blogs
  • Magazine, journal, and newspaper articles
  • Research reports and conference papers
  • Field notes and diaries

And much more

With so many sources available, the question usually is not whether sources exist for your project but which ones will best meet your information needs. Being able to categorize a source helps you understand the kind of information it contains, which is a big clue to (1) whether might meet one or more of your information needs and (2) where to look for it and similar sources. Understanding how information can be categorized can be helpful; remember that sources can be in more than one category at the same time as categories are not always mutually exclusive.

Intended Audience: Scholarly, Popular and Professional Sources

One way to categorize information is by the expertise of its intended audience. Considering the intended audience—how expert one has to be to understand the information—can indicate whether the source has sufficient credibility and thoroughness to meet your need.

There are varying degrees of expertise: Scholarly, Popular and Professional. See a summary of each at the tabs along the right.

Immediately below, see a useful video on the parts of a Scholarly journal article. Try the self-assessment exercise immediately below that!

Scholarly – Scholarly journal articles (such as those published in the journals Plant Science and Education and Child Psychology) are meant for scholars, students, and the general public who want a deep understanding of a problem or issue. Researchers and scholars write these articles to present new knowledge and further understanding of their field of study.

Additionally, they are:

  • Where findings of research projects, data and analytics, and case studies usually appear first.
  • Often long (usually over 10 pages) and always include footnotes and references.
  • Usually published by universities, professional associations, and commercial publishers.
  • Published after approval by peer review or from the journal’s editor

Scholarly information can also come in the form of books, particularly in the humanities and some social sciences. These can be in monograph form (an extended analysis of a single topic by a single or several authors) or in an edited volume (where many authors contribute different takes on a theme, each writing up a contributory chapter).

The value of scholarly journals

Articles in scholarly journals are valued for several reasons. First, they are usually trustworthy because their publication process includes a peer review that helps insure their accuracy and contribution to their disciplines. In addition, they often contain the first reports of new research, which makes their sections on methodology, data, analysis, and interpretation primary sources. Sometimes they instead consist of literature reviews summaries of multiple research studies done in the past on particular subjects of current interest. That makes those articles very helpful secondary sources.

Peer-Reviewed Sources

The most-respected scholarly journals are peer-reviewed, which means that experts in their field other than the author and editor check out each article before it can be published. It’s their responsibility to help guarantee that new material is presented in the context of what is already known, that the methods the researcher used are the right ones, and that the article contributes to the field. For those reasons, peer-reviewed articles are more likely to be credible. Peer-reviewed journal articles are the official scholarly record, which means that if it’s an important development in research, it will probably turn up in a journal article eventually.

Finding Scholarly Articles

Most scholarly articles are housed in specialized databases. Libraries (public, school, or company) often provide access to scholarly databases by paying a subscription fee for patrons. For instance, NUI Galway Library provides access to dozens of databases which can be found via the Library Catalogue on the homepage or the subject-specific Library Guides. Databases that aren’t subject-specific are called general databases. Google Scholar is a free general scholarly database available to all who have access to the Internet, and it provides some scholarly articles.

Popular newspaper and magazine articles (such as those found in The Irish Times, the New Yorker, and Hot Press) are meant for a large general audience, are generally affordable, and are easy to purchase or available for free. They are written by staff writers or reporters for the general public.

Additionally, they are:

  •     About news, opinions, background information, and entertainment.
  •     More attractive than scholarly journals, with catchy titles, attractive artwork, and many advertisements but no footnotes or references.
  •     Published by commercial publishers.
  •     Published after approval from an editor.

Professional magazine articles (such as those found in the magazines Plastic Surgical Nursing and Music Teacher) are meant for people in a particular profession, and are often accessible through a professional organization. Staff writers or other professionals in the targeted field write these articles at a level and with the language to be understood by everyone in the profession.

Additionally, they are:

  •     About trends and news from the targeted field, book reviews, and case studies.
  •     Often less than 10 pages, some of which may contain footnotes and references.
  •     Usually published by professional associations and commercial publishers.
  •     Published after approval from an editor.


Formats and The Information Life Cycle

We can also categorize sources by publication format. That’s because of the difference in time and effort sources in each format require for their production.

Different formats would include things like books, journal articles, magazine articles, newspapers, social media, and television and film documentaries. Sources in particular formats simply cannot exist until there has been enough time for people to create them.

The result is that the sources that are created toward the end of the information lifecycle may come to very different conclusions about the event than did those sources created early on. Sometimes the information presented in the later formats is more valid and reliable that what is in those produced earlier. Play the following short video from University of Las Vegas libraries for more information on the Information Life Cycle.

Primary, Secondary or Tertiary Information

Another information category is called publication mode and has to do with whether the information is

  • Firsthand information (information in its original form, not translated or published in another form).
  • Secondhand information (a restatement, analysis, or interpretation of original information).
  • Third-hand information (a summary or repackaging of original information, often based on secondary information that has been published).

The three labels for information sources in this category are, respectively, primary sources, secondary sources, and tertiary sources. Here are examples to illustrate the first- handedness, second-handedness, and third-handedness of information:

Primary Source: The novel Amongst Women by author John McGahern

Secondary Source: A scholarly article analyzing passages from the novel Amongst Women.

Tertiary Source: A Wikipedia article about John McGahern.

When you make distinctions between primary, secondary, and tertiary sources, you are relating the information itself to the context in which it was created. Understanding that relationship is an important skill that you’ll need in college, as well as in the workplace. Noting the relationship between creation and context helps us understand the “big picture” in which information operates and helps us figure out which information we can depend on. That’s a big part of thinking critically, a major benefit of actually becoming an educated person.

Primary Sources – Because it is in its original form, the information in primary sources has reached us from its creators without going through any filter. We get it firsthand. Here are some examples that are often used as primary sources:

  • Any literary work, including novels, plays, and poems.
  • Breaking news.
  • Diaries.
  • Advertisements.
  • Music and dance performances.
  • Eyewitness accounts, including photographs and recorded interviews.
  • Artworks.
  • Data.
  • Blog entries that are autobiographical.
  • Scholarly blogs that provide data or are highly theoretical, even though they contain no autobiography.
  • Artifacts such as tools, clothing, or other objects.
  • Original documents such as tax returns, marriage licenses, and transcripts of trials.
  • Websites, although many are secondary.
  • Buildings.
  • Correspondence, including email.
  • Records of organizations and government agencies.
  • Journal articles that report research for the first time (at least the parts about the new research, plus their data).

Secondary Source – These sources are translated, repackaged, restated, analyzed, or interpreted original information that is a primary source. Thus, the information comes to us secondhand, or through at least one filter. Here are some examples that are often used as secondary sources:

  • All nonfiction books and magazine articles except autobiography.
  • An article or website that critiques a novel, play, painting, or piece of music.
  • An article or web site that synthesizes expert opinion and several eyewitness accounts for a new understanding of an event.
  • The literature review portion of a journal article.

Tertiary Source – These sources further repackage the original information because they index, condense, or summarize the original.

Typically, by the time tertiary sources are developed, there have been many secondary sources prepared on their subjects, and you can think of tertiary sources as information that comes to us “third-hand.” Tertiary sources are usually publications that you are not intended to read from cover to cover but to dip in and out of for the information you need. You can think of them as a good place for background information to start your research but a bad place to end up. Here are some examples that are often used as tertiary sources:

  • Almanacs.
  • Dictionaries.
  • Guide books, including the one you are now reading.
  • Survey articles.
  • Timelines.
  • Bibliographies.
  • Encyclopedias, including Wikipedia.
  • Most textbooks.

Tertiary sources are usually not acceptable as cited sources in college research projects because they are so far from firsthand information. That’s why most professors don’t want you to use Wikipedia as a citable source: the information in Wikipedia is far from original information. Other people have considered it, decided what they think about it, rearranged it, and summarized it–all of which is actually what your professors want you, not another author, to do with information in your research projects.

A few things about primary or secondary sources to remember:

  • Sources become primary rather than always exist as primary sources

It’s easy to think that it is the format of primary sources that makes them primary. But that’s not all that matters. So when you see lists like the one above of sources that are often used as primary sources, it’s wise to remember that the ones listed are not automatically already primary sources. 

  • Primary sources, even eyewitness accounts, are not necessarily accurate. Their accuracy has to be evaluated, just like that of all sources.
  • Something that is usually considered a secondary source can be considered a primary source, depending on the research project.

For instance, movie reviews are usually considered secondary sources. But if your research project is about the effect movie reviews have on ticket sales, the movie reviews you study would become primary sources.

Deciding whether to consider a journal article a primary or a secondary source can be complicated for at least two additional reasons.

First, journal articles that report new research for the first time are usually based on data. So some disciplines consider the data to be the primary source, and the journal article that describes and analyzes them is considered a secondary source.

However, particularly in the sciences, the original researcher might find it difficult or impossible (he or she might not be allowed) to share the data. So sometimes you have nothing more firsthand than the journal article, which argues for calling it the relevant primary source because it’s the closest thing that exists to the data.

Second, even journal articles that announce new research for the first time usually contain more than data. They also typically contain secondary source elements, such as a literature review, bibliography, and sections on data analysis and interpretation. So they can actually be a mix of primary and secondary elements. Even so, in some disciplines, a journal article that announces new research findings for the first time is considered to be, as a whole, a primary source for the researchers using it.

What are considered primary and secondary sources can vary from discipline to discipline. If you are required to use primary sources for your research project, before getting too deep into your project check with your professor to make sure he or she agrees with your choices. After all, it’s your professor who will be grading your project.

Quantitative and Qualitative

One of the most obvious ways to categorize information is by whether it is quantitative or qualitative. Some sources contain either quantitative information or qualitative information, but sources often contain both.

Many people first think of information as something like what’s in a table or spreadsheet of numbers and words. But information can be conveyed in more ways than textually or numerically.

Qualitative Information – Involves a descriptive judgment using concept words instead of numbers. Gender, country name, animal species, and emotional state are examples of qualitative information.

Quantitative Information – Involves a measurable quantity—numbers are used. Some examples are length, mass, temperature, and time. Quantitative information is often called data, but can also be things other than numbers.

Increasingly, other formats (such as images, sound, and video) may be is used as information or used to convey information. Some examples:

  • A video of someone watching scenes from horror movies, with information about their heart rate and blood pressure embedded in the video. Instead of getting a description of the person’s reactions to the scenes, you can see their reactions.
  • A database of information about birds, which includes a sound file for each bird singing. Would you prefer a verbal description of a bird’s song or an audio clip?
  • A list of colors, which include an image of the actual color. Such a list is extremely helpful, especially when there are A LOT of color names.
  • A friend orally tells you that a new pizza place is 3 blocks away, charges $2 a slice, and that the pizza is delicious. This may never be recorded, but it may be very valuable information if you’re hungry!
  • A map of Ohio with counties shaded different intensities of red according to the median household income of inhabitants.