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Environmental Science and Studies Research Guide

This guide serves all of Iowa State's environmental programs as well as the many courses that share themes of sustainability, resource management, and environmental awareness.

Evaluating Information

Use critical thinking to decide when information is useful, trustworthy, and relevant.

Not all information is created equal

Searching and locating information sources is only one part of the research process. An equally important part is being able to tell if the sources you've located are trustworthy, appropriate, and authoritative.

Sliding Scales

Source evaluation is along sliding scale; not black or white, good or bad. While there are some sources a majority will agree are "good" or "bad" most information falls somewhere in between these two extremes.

How Much You Can Trust a Bearded Man?
A silly example of a sliding scale, The Trustworthiness of Beards by Matt McInerney. Click to enlarge.

Evaluating Sources with S.I.F.T.

SIFT is a helpful acronym that describes four steps that can be used to evaluate information sources. This version on this page is a short overview that can be used for quick reference. For the full version, and for more information and guidance about how and why to evaluate information sources, see the Chapter 4 of the Library 160 textbook (open access).


  • Check yourself. Recognize your own biases, beliefs, and potential blind spots and acknowledge that they will effect your judgment.
  • Stay on task. It is easy to get lost exploring interesting tangents while researching. If this happens stop and remember your original purpose. 

Investigate the Source

  • Who dis? You need to trust the authors and publisher if you plan to use a source. What is their reputation? How is the information presented (fact or opinion)? What's background? Are there any conflicts of interest?

Find better coverage

  • What else is out there? Before using a source check to see if the topic has been covered elsewhere. Has anyone else written about it? Do other publications provide more information? Do they tell the same story and contain the same facts? Try to locate additional sources that are more detailed, varied, transparent, authoritative, and/or build upon the information presented in your initial source.

Trace it back.

  • Context matters. Before trusting or reusing information, look for the original source. Who first wrote about the topic? When was it first published? Is it accurate? At this point, you may need to repeat steps I and F in order to evaluate a new information source.
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Megan O'Donnell
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