Evidence aspect of critical thinking examined and discussed. Also, the importance of the credibility of any given evidence.

1. TYPES OF EVIDENCE &
UNDERSTANDING
CREDIBILITY
Margot Cooper
Gruen

2. THERE ARE 5 T YPES OF EVIDENCE IN A
CRITICAL THINKING CONTEXT:
Precedent Evidence
Statistical Evidence
Testimonial Evidence
Hearsay Evidence
Common Knowledge Evidence

3. PRECEDENT EVIDENCE
Precedent evidence consists of two forms: legal and personal .
 Legal precedent is the application of prior judicial decisions
to new case. Precedents are generally rarely changed, due to
the fact that it becomes a „standard‟ in court and attempts to
make judicial decisions uniform in nature.
 The Ohio State Bar Association explains why judges follow
precedent:

4. Via: Ohio Bar

5. P E R S O N A L P R E C E D E N T I S M A K I N G I N F E R E N C E S B A S E D O N PA S T R E S U LT S .
F O R E X A M P L E , L I V I N G I N L O S A N G E L E S , YO U K N O W YO U W I L L M O S T
L I K E LY G E T A T I C K E T I F YO U PA R K I L L E G A L LY.
Via: Youtube

6. STATISTICAL EVIDENCE
Statistical Evidence is presented in the form of numerical facts. Although many people
believe statistics to be infallible, this is far from the truth. Statistics can be misleading,
because although they attempt to be objective, there are few cases where this is
completely accurate.
Scholar and professor at Augsburg College, Milo Schield wrote an article titled;
“Statistical literacy: Thinking critically about statistics.” He mentions some key points
regarding statistics and critical thinking.
“Statistical literacy focuses on making decisions using statistics as evidence just as
reading literacy focuses on using words as evidence. Statistical literacy is a
competency just like reading, writing or speaking. Statistical literacy involves two
reading skills: comprehension and interpretation.”
He also goes on to discuss three important distinctions within the field of statistical
evidence: association versus causation, sample versus population, and quality versus
power of a test. It is shown by all of these factors that statistical evidence should be
put under just as much scrutiny as any other type of evidence.

7. SATIRICAL STATISTICS
An article by William Saletan on Slate.com lists some studies and their results with a
satire edge. One of them:
Evolution favors female promiscuity. In a study of mouse-like
marsupials, "survival of babies with promiscuous mothers was almost
three times as high as those in the monogamous group." Key reasons:
1) "The sperm of some males were far more successful than others."
2) "Babies fathered by these males were twice as likely to survive."
Takeaway for women: "Polyandry improves female lifetime fitness."
Takeaway for men: "Males with more competitive ejaculates sire more
viable offspring." Fine print: "Males usually died after a short and
intense single mating season due to exhaustion and aggressive
encounters with other males." (Did we mention that female
promiscuity promotes big testicles and small brains in males?)
Via: Slate

8. TESTIMONIAL EVIDENCE
Testimonial evidence consists of a person‟s testimony (opinion
of reality). Generally when using evidence, it is preferable to
put importance on provable facts rather than opinion or
recollection. The three types of testimonial evidence are:
1. Eyewitness
2. Expert-witness
3. Historiography

9. EYEWITNESS
1. Eyewitness – person who saw something take place‟s
recollection. This type of evidence has inherent flaws, as everyone
has a different „reality.‟
In Problems and Materials on Trial Advocacy, authors Levin &
Cramer discuss eyewitness testimony:
“Eyewitness testimony is, at best, evidence of what the witness
believes to have occurred. It may or may not tell what actually
happened. The familiar problems of perception, of gauging time,
speed, height, weight, of accurate identification of persons accused
of crime all contribute to making honest testimony something less
than completely credible.”

10. EXPERT-WITNESS
2. Expert-witness – This type of testimony is consists of declarations from people
considered „professionals‟ in a given field. Even within this type of testimony,
professionals can disagree and are still subject to bias.
According to the Legal Information Institute, a group within Cornell Law School, the
following are general rules for expert witness testimony:

11. HISTORIOGRAPHY
3. Historiography – This testimony is presented by a historian. In the article
“The Historian‟s Valuable Role as Expert and Advisor in Environmental
Litigation” authors state:
“Retaining a professional historian as an expert witness, can be
useful in avoiding the limited perspective and fading memories
of eyewitnesses and the perception of bias associated with
advocates relating historical facts. Historian experts, similar to
their counterparts in the hard sciences, employ specialized
contextual knowledge and a disciplined methodology in their
research and analysis, and use a customized and targeted
approach to effectively gather and synthesize the available
historical evidence and to relate historical facts in a thorough
and compelling manner.”

12. HEARSAY EVIDENCE
Hearsay Evidence consists of rumors or gossip that are
repeated among multiple people. This type of evidence is
mostly used in non-formal arguments, when lack of other
types of evidence are present. Hearsay can also be used to
determine motives, or at least open the door to some ideas.
The clip on the next slide from The Daily Show with Jon
Stewart provides an example of the „powerful‟ evidence of
hearsay, tied into a news story about school curriculums and
race:

13. Via: The Daily Show

14. COMMON KNOWLEDGE EVIDENCE
Common Knowledge Evidence consists of using information that
is readily accepted by (mostly) everyone. This information is
generally uncontested, so it is most useful in non confrontational or non-controversial arguments.

15. CREDIBILIT Y
 With all the dif ferent types of evidence that can be presented
to make a case or claim, it is crucial that as a critical thinker,
the credibility of evidence presented is evaluated closely. As
outlined with each type of evidence, there is the possibility for
fault many steps of the way.
 Critical thinkers should strive to develop skills that question
information. Carl Sagan, an astronomer and scientist, is
quoted, “Extraordinary claims require extraordinary evidence.”
He also explained that critical thinkers need be skeptical, but
also open minded.
The next slides outline a speech by Sagan that examines the
balance required between skepticism and open -mindedness:

16. CARL SAGAN QUOTE
It seems to me what is called for is an exquisite balance between
two conflicting needs: the most skeptical scrutiny of all hypotheses
that are served up to us and at the same time a great openness to
new ideas. Obviously those two modes of thought are in some
tension. But if you are able to exercise only one of these modes,
whichever one it is, you‟re in deep trouble .
If you are only skeptical, then no new ideas make it through to you.
You never learn anything new. You become a crotchety old person
convinced that nonsense is ruling the world. (There is, of course,
much data to support you.) But every now and then, maybe once in
a hundred cases, a new idea turns out to be on the mark, valid and
wonderful. If you are too much in the habit of being skeptical
about everything, you are going to miss or resent it, and either way
you will be standing in the way of understanding and progress.

17. CARL SAGAN QUOTE CONT.
On the other hand, if you are open to the point of gullibility and
have not an ounce of skeptical sense in you, then you cannot
distinguish the useful as from the worthless ones. If all ideas
have equal validity then you are lost, because then, it seems to
me, no ideas have any validity at all .
Some ideas are better than others. The machinery for
distinguishing them is an essential tool in dealing with the
world and especially in dealing with the future. And it is
precisely the mix of these two modes of thought that is central
to the success of science.
Via: Brain Pickings

18. EVALUATING AS A CRITICAL THINKER
Evaluating information consists of differentiating facts
and opinions, recognizing generalizations and biased
language.
Critical thinkers should be skeptical, question
everything. The quality of information, the rationality
of information, the biases and prejudices inherent in
people, and the motive behind content presented.

19. QUOTES
“The essence of the
independent mind
lies not in what it
thinks, but in how it
thinks.”
― Christopher
Hitchens, Letters to
a Young Contrarian

20. QUOTES
A wise man
proportions his belief
to the evidence.
– David Hume

21. LASTLY, A VIDEO FOR ARTISTIC PURPOSES OF
SHOWING HOW EVIDENCE WAS GATHERED FOR
A STUDY IN DENMARK.
(Click to View)

22. CITATIONS
 Reis, Michael C., and W. David Wiseman Jr. "The Historian‟s
Valuable Role as Expert and Advisor in Environmental
Litigation." Environmental Litigator. 22.3 (2011): 12-14. Print.
<http://www.historyassociates.com/wpcontent/uploads/2012/06/HistoryAssociates_Historians_Role
_As_Expert.pdf>.
 Schield, Milo. "Statistical literacy: Thinking critically about
statistics." Of Significance 1 .1 (1999): 1520.http://web.augsburg.edu/~schield/MiloPapers/ 984Statisti
calLiteracy6.pdf