Teaching Critical Thinking
Understanding & Evaluating Evidence: Reliability

Evaluating evidence includes deciding whether it is reliable, relevant and of sufficient quantity.  This section examines reliability: Is evidence trustworthy? Is it cited accurately? 

Assignments and Activities
Note: (L) Can be done in large section courses

Identifying Evidence

Explain that evidence consists of reported facts and examples, statistics, the opinions of experts, and previously established sub-claims.  Have students read an article, listen to a speech or visit a web page that makes a straightforward case in support of a clearly stated claim, then ask them to complete the following table:

Main Claim:
Sub-claim: (Stated or Implied) Evidence for Sub-claim
     
  
  
       
    
  
etc...... etc......

If students are uncertain what sub-claim evidence is meant to support, they should list it in the “evidence” column without a corresponding sub-claim.  Discuss students’ responses; if wished, compare them to a key provided by the instructor. (L)

Fact-Checking

Explain that “fact-checking” is a routine part of journalistic writing and book publishing.  It means confirming that the “facts” cited in a forthcoming article or book are accurate. (For a fact-checking web site that working journalists use, see http://www.journaliststoolbox.com/newswriting/general.html)  Then assign students to fact-check a web site or article relevant to the course, preferably one with some plausible-looking “facts” that are inaccurate or fabricated.  This assignment is also useful in demonstrating the importance of footnoting to students, who will discover that fact-checking is much easier when accurate citations are available. (L)

Evaluating Kinds of Evidence

Discuss how to judge the reliability of the kinds of evidence most often encountered in your course.  Then divide the class into pairs or groups and assign each pair or group to evaluate one kind of evidence (e.g., facts, statistics, examples, opinion evidence) in a sample argument.  Discuss students’ findings and/or compare them to a key provided by the instructor. If wished, create check lists for students to use, such as the one below for opinion evidence:

Main Claim:

Sub-claim

Opinion Evidence
(one piece per cell)

Tests of Reliability

  • Authority is qualified with respect to issue
  • Authority has direct knowledge of issue
  • Authority is unbiased with respect to issue
  • Opinion is timely
  • Quoted accurately and in context
  • Complete citation provided
etc.. etc.. etc..

(L) Can be done in large section courses