Non-academic sources are very valuable for scholarly research, especially in the humanities and social sciences. The challenge in using them lies in the fact that they haven’t gone through a more-or-less fixed process of quality checking before they become available, as is the case with scholarly sources (i.e. academic publications).
Also, the places where you find these sources, the public library but even more so the free web (Google and other search engines) lack the quality filters that are available to you in academic databases and academic search engines. This means the only quality checker is YOU!
There are four important criteria by which to evaluate sources:
This criteria is especially important when it comes to online sources. Since anyone can publish anything on the Internet, it’s important to find out if the author has any authority on the topic he/she is writing on, or to make certain pronouncements.
The goal of this part of the checklist is checking the source for correctness, whereby you look into matters such as verifiable facts, how current the source is and whether or not it paints a complete picture.
3. Reasonableness (objectivity)
A credible source strives for objectivity and also pays attention to counter-arguments. What is the purpose of the source? Is there bias?
There are very few sources which constitute original work. Even literary works (novels, plays, poetry) often build upon older literature. This means that almost all texts that you find are actually rephrasing and interpreting other texts. Are these original sources mentioned or listed in the source you found? Often this will not be the case. With literary texts this is (in most cases) not a problem, as we know the author by name (Credibility check) and won't use a novel or poem to collect factual information. But even when you are looking for non-literary sources and the one you find lacks (a) direct link(s) to the original source(s) on which is is based (as reference in the text itself, in a footnote or bibliography, or as a hyperlink), in many cases you can still find indications that the text is based on sources, and not just the creative thoughts of the author alone. Notice for example the source acknowledgment in the following paragraph from an online article:
Source: Epstein, Alex (2015, January 6). '97% of climate scientists agree' is 100% wrong. Retrieved from https://www.forbes.com/sites/alexepstein/2015/01/06/97-of-climate-scientists-agree-is-100-wrong/#4ff61cfa7187.
When sources are mentioned, you should evaluate these just as you did with the source you are interested in. If the majority of the mentioned sources are unsound, this is a strong indication that your source is of low quality and you might not want to use it.
There are very few non-academic sources that score 100 percent on all criteria. This is not a problem. In some cases you might actually be looking for sources that score low on a certain criterium. If, for example, you research public opinion, sources that score low on reasonableness (objectivity) are just what you want. But even then it is important to keep the criteria in the back of your mind. In the above case, for instance, you should know what the authority (credibility) of the author is within his or her “camp” (progressive/conservative, left wing/right wing, etc.). To learn more about this, check the module Verifying credibility of non-academic online sources.
Tip: There are many useful criteria checklists similar to the above CARS, such as CRAAP (Currency, Relevance, Authority, Accuracy and Purpose) and ASPECT (Authority, Sources, Purpose, Evenness, Coverage and Timeliness).