Every subject is a little different, and so how you evaluate sources for that subject differs. There is no easy checklist or one-size-fits-all approach to see if a source is credible or reliable. There are, however, some basic guidelines that can get you started. As with all information resources, the usefulness of the information may depend on the guidelines for an assignment or the ultimate goal of your research. Here is a helpful acronym to provide a basic guideline, and then some specifics, complete with questions, follow.
Objectivity, Bias, or Point of View
What is the objective of the author writing this work?
Does the page display a particular bias or perspective? Is it clear and forthcoming about its view of the subject? Does it use inflammatory or provocative language? Does the author maintain neutral language?
If there is bias, is it unconscious bias or conscious bias?
If there is conscious bias, is there a reason that the author demonstrates this inclination?
If the page contains advertising, are the ads clearly distinguishable from the content?
Is any conflict of interest discernable between content and advertising?
Is the author using rhetorical strategies to get you to "buy in" to the ideas they present?
Is this up to date?
Is it clear when the information was published and when was it last updated?
When was the research conducted?
Is this the most recent version?
For websites, are the pages current?
If there are links to other websites, are they current?
Are there more recent events that might color the information's findings?
(For some disciplines, you may wish to compare one iteration of an idea from the past with a new iteration in the present. If that is the case, then the dates that you choose will vary. In addition, you may be searching for primary source materials, and then you are not looking for current information but rather past information. Remember, use these questions as guidelines, not as a one-size-fits-all approach.)
Are the sources I have found actually relevant to my topic?
What is the main topic or idea of the resource?
Will this resource be helpful in answering my research question?
Can this resource help me refine my topic?
(It is important to note that databases also have inherent bias toward Caucasian, male authors, so be aware of this when looking at search results.)
Who wrote this?
Is the author clearly identified? What are his or her credentials for writing on this topic? In other words, is the author an expert in their field?
Can the author speak about a topic based on life experience, lending expertise in this manner? (This is especially important for primary sources.)
Is the author affiliated with an organization? If so, what is the reputation of that organization?
Is there a link back to the organization's page or some other way to contact the organization and/or verify its credibility? (e.g. address, phone number, e-mail address, “About” page, etc.)
For websites, who publishes and/or is responsible for the website itself? Who has registered the URL? Does that organization have any blatant bias or agenda?
Do they give me proof?
Is the page part of an edited or peer-reviewed publication?
Does the content of the page convey the amount, depth, and significance of the evidence being presented?
Are the arguments persuasive? How or in what way?
Can factual information be verified through footnotes or bibliographies to other credible sources?
Did you find this source using an internet search engine such as Google or Bing? They neither select the best pages nor filter out questionable ones, so you need to evaluate the choices carefully. (Remember that people pay to have their sites show up early in Google's search results, so the early results are not necessarily going to be the best results for your topic.)
Based on what you already know about the subject (or have checked from other sources), does this information seem credible?
Are there obvious typos or misspelled words or other signs of sloppiness? (This often indicates amateur work, but it could be due to English not being an author's first language, so research the author.)
Why does this exist?
Are the purpose and objectives of the page clear?
Is the primary purpose to provide information? Is it to sell a product? Is it to make a political point? Is it to have fun? Is it to parody a person or organization or idea?
Is there a stated purpose, but then an actual purpose behind the information?
Who put this out there?
Where was this published?
How does the publication's authority affect the information's credibility? (e.g. university press, political organization, etc.)
What is the URL?
.org - This is used for non-profits, and such organizations often have solid information based on data, but beware, just because a group is a non-profit does not mean that the information is reliable. Non-profit is an IRS designation and is not a guarantee about the information presented. So, it is still important to look for other sources that back up the claims being made.
.edu - This is used for higher educational institutions, such as colleges and universities. You will often find reliable information from these sites, but beware, sometimes there are sites that contain student work that is NOT reliable. Again, you always want to find other sources that back up the claims being made.
.com - This is used for commercial sites that are trying to sell you products or ideas. These often do NOT have reliable information, so it is very important to find other reliable sources that back up any claims being made.
.gov - This is used by the government. Many government sites contain reliable information, such as labor statistics, updated guidelines for the FDA, raw data that can be helpful with research, and a lot of other important information. It is still important, however, to double-check the data, as typos or errors do sometimes occur (or occasionally unscrupulous individuals are providing content.)
.net - This was originally used as an Intranet designation within organizations who had their own internal systems, but it has come to be used by organizations that often do not fall into the other categories (e.g. K-12 school districts). The designation is still a top-level domain designation like the others listed above.
Who is interested?
Is it geared to a particular audience, expertise, geographic region, period of time, or another factor/group?
Is it a comprehensive resource, or does it focus on a narrow range of information? Is it clear about this focus?
If it is an information database, are the dates of coverage clear and appropriate to your needs? Is it easy to search? Does it present information in a usable format?
Other Items to Consider:
Integrity of the Data
Is the source of any factual information clearly stated?
Are the source, scope, and date of any statistics clearly labeled?
Is it clear whether or not the information has been excerpted from a larger piece?
Is there a way to tell if this is the most recent version of a particular piece?
Does the author rely on photographic images to make a point? If so, be aware that digital images can be easily manipulated.