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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.

What it is and how it's used matter

Source evaluation happens along a sliding scale - in other words, "good" and "bad" are conditional. What you need information for and how you intend to use it is just as important as who wrote it and how experienced they are.

For example, if I want to know how many people live in Ames I can easily get a number from Wikipedia to satisfy my curiosity. But if I plan to use that number in a report then I need to verify the number using a more trusted information source, such as the latest U.S. Census data.

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 made it? You need to trust the authors and publisher if you plan to use a source. What is their reputation? How is the information presented? Is it based on facts or is it an opinion? Are they experts? Are there any conflicts of interest that might bias the information?

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 but don't worry, it shouldn't take long and you're getting good at this. 
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Lorrie Pellack
Head, Research & Instruction Services Dept.
150c Parks Library
Ames, IA 50011-2140
Phone: 515-294-5569