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Evaluating Sources: General Guidelines

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Once you have an idea of the types of sources you need for your research, you can spend time evaluating individual sources. If a bibliographic citation seems promising, it’s a good idea to spend a bit more time with the source before you determine its credibility. Below are some questions to ask and things to consider as you read through a source. 

Find Out What You Can about the Author

One of the first steps in evaluating a source is to locate more information about the author. Sometimes simply typing an author’s name into a search engine will give you an initial springboard for information. Finding the author’s educational background and areas of expertise will help determine whether the author has experience in what they’re writing about. You should also examine whether the author has other publications and if they are with well-known publishers or organizations.

Read the Introduction / Preface

Begin by reading the Introduction or the Preface—What does the author want to accomplish? Browse through the Table of Contents and the Index. This will give you an overview of the source. Is your topic covered in enough depth to be helpful? If you don't find your topic discussed, try searching for some synonyms in the Index.

If your source does not contain any of these elements, consider reading the first few paragraphs of the source and determining whether it includes enough information on your topic for it to be relevant.

Determine the Intended Audience

Consider the tone, style, vocabulary, level of information, and assumptions the author makes about the reader. Are they appropriate for your needs? Remember that scholarly sources often have a very particular audience in mind, and popular sources are written for a more general audience. However, some scholarly sources may be too dense for your particular research needs, so you may need to turn to sources with a more general audience in mind.

Determine whether the Information is Fact, Opinion, or Propaganda

Information can usually be divided into three categories: fact, opinion, and propaganda. Facts are objective, while opinions and propaganda are subjective. A fact is something that is known to be true. An opinion gives the thoughts of a particular individual or group. Propaganda is the (usually biased) spreading of information for a specific person, group, event, or cause. Propaganda often relies on slogans or emotionally-charged images to influence an audience. It can also involve the selective reporting of true information in order to deceive an audience.


  • Fact: The Purdue OWL was launched in 1994.
  • Opinion: The Purdue OWL is the best website for writing help.
  • Propaganda: Some students have gone on to lives of crime after using sites that compete with the Purdue OWL. The Purdue OWL is clearly the only safe choice for student writers.

The last example above uses facts in a bad-faith way to take advantage of the audience's fear. Even if the individual claim is true, the way it is presented helps the author tell a much larger lie. In this case, the lie is that there is a link between the websites students visit for writing help and their later susceptibility to criminal lifstyles. Of course, there is no such link. Thus, when examining sources for possible propaganda, be aware that sometimes groups may deploy pieces of true information in deceptive ways.

Note also that the difference between an opinion and propaganda is that propaganda usually has a specific agenda attached—that is, the information in the propaganda is being spread for a certain reason or to accomplish a certain goal. If the source appears to represent an opinion, does the author offer legitimate reasons for adopting that stance? If the opinion feels one-sided, does the author acknowledge opposing viewpoints? An opinion-based source is not necessarily unreliable, but it’s important to know whether the author recognizes that their opinion is not the only opinion.

Identify the Language Used

Is the language objective or emotional? Objective language sticks to the facts, but emotional language relies on garnering an emotional response from the reader. Objective language is more commonly found in fact-based sources, while emotional language is more likely to be found in opinion-based sources and propaganda.

Evaluate the Evidence Listed

If you’re just starting your research, you might look for sources that include more general information. However, the deeper you get into your topic, the more comprehensive your research will need to be.

If you’re reading an opinion-based source, ask yourself whether there’s enough evidence to back up the opinions. If you’re reading a fact-based source, be sure that it doesn’t oversimplify the topic.

The more familiar you become with your topic, the easier it will be for you to evaluate the evidence in your sources.

Cross-Check the Information

When you verify the information in one source with information you find in another source, this is called cross-referencing or cross-checking. If the author lists specific dates or facts, can you find that same information somewhere else? Having information listed in more than one place increases its credibility.

Check the Timeliness of the Source

How timely is the source? Is the source twenty years out of date? Some information becomes dated when new research is available, but other older sources of information can still be useful and reliable fifty or a hundred years later. For example, if you are researching a scientific topic, you will want to be sure you have the most up-to-date information. However, if you are examining an historical event, you may want to find primary documents from the time of the event, thus requiring older sources.

Examine the List of References

Check for a list of references or other citations that look as if they will lead you to related material that would be good sources. If a source has a list of references, it often means that the source is well-researched and thorough.

As you continue to encounter more sources, evaluating them for credibility will become easier.