Generalization and
Argument by Example
forms of inductive
reasoning
argument from generalization
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Generalizations are one of the most common
forms of reasoning.
Definition: Generalizing involves attempts to
identify general patterns, gauge what is typical or
average, or formulate general rules
Generalizing is necessary, indispensable
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Imagine what life would be like if you couldn’t form
generalizations--if all knowledge was particularized
and fragmented.
Generalizing is also fraught with risks
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Think how many false stereotypes people hold about
race, gender, age, etc.
What if Jim Abbot had believed people who said you
couldn’t pitch in the major leagues with only one arm?
What if Stephen Hawking presumed that a person in a
wheelchair couldn’t be a leading theoretical physicist?
Bondes are dumb?
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Blondes are dumb?
– Does the stereotype refer only to
natural blondes? Does the
stereotype only to female, not
male blondes?
– Reese Witherspoon attended
Stanford and won an oscar.
– Hillary Clinton, law degree from
Yale
– Lisa Kudrow, degree in biology
from Vassar
– Sharon Stone has a reported IQ
of 154
– Kim Campbell, Canada’s first
female prime minister, is blonde.
White men can’t jump?
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Does the stereotype only
apply to basketball?
Andrey Silnov, a Russian, won
the gold medal in the high jump
in Beijing in 2008.
Javier Sotomayor, a Cuban has
the current world record in the
men’s high jump.
Patrick Sjöberg of Sweden has
the 2nd highest world record in
the high jump
Igor Paklin, a Russian, has the
3rd place world record,
Rudolph Povarnitsyn, another
Russian, is 4th best.
Andrey Silnov
Asians are bad drivers?
Percenta
ge of
deaths
from
traffic
fatalities
African
or
Black
Anglo
or
White
Asian
and
Pacific
Islande
r
Hispani
c or
Latino
Native
Americ
an
1.8
1.6
2.5
4.7
6.8
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Does the stereotype apply to all
Asians, or only some?
Are Taiwanese better than
Japanese or Vietnamese or
Korean drivers? Does it apply to
2nd or 3rd generation AsianAmericans?
A study by the NHTSA published
in 2006 revealed that Asian
drivers were not responsible for a
disproportionate share of fatal
accidents
As a percentage of the population
Hispanics and Native Americans
accounted for more fatal crashes.
An “Indian” kid always wins the
spelling bee?
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An “Indian” kid (sub-Asian continent)
always wins the national spelling bee?
4 of the past 9 winners were of Indian
descent
National Spelling Bee Winners Since
2000
2008 Sameer Mishra
2007 Evan O’Dorney
2006 Katharine “Kerry” Close
2005 Anurag Kashyap
2004 David Scott Pilarski Tidmarsh
2003 Sai R. Gunturi
2002 Pratyush Buddiga
2001 Sean Conley
2000 George Abraham Thampy
Polling and surveys as a form of
generalizing
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Public opinion polls
Nielsen ratings for TV shows
American Idol voting
ratemyprofessor.com
call-screening on radio talk shows
To be truly valid a sample should be:
– random
– representative
– sufficient in size.
universal and statistical
generalizations
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Universal generalization: claims that all members of a group have certain
attributes or characteristics
– Asians are good at math.
Feminists hate men.
– Republicans favor tax cuts, Democrats oppose tax cuts.
Statistical generalization: claims that a percentage or a portion of a group has
a certain attribute or property.
– 76% of felons are recidivists
– 1 out of 3 children in the U.S. is born out of wedlock
– 19 of the 21 hijackers on Sept. 11 were Saudi Arabians.
Contingent generalization: based on conditions or qualifications that must be
met for the generalization to hold true. Generalizations are more likely to
hold true if they are confined to specific times, places, or situations
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Most serial killers are male
The majority of journalists are Democrats
inductive and deductive
generalizations
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Two types of generalizations: inductive and deductive
Inductive Generalization: bases a larger inference on an
example, sample, or particular instance
– example: Babbs bought a Saturn and it runs well. Biff
bought a Saturn and it runs well. I guess Saturns are
reliable cars. (the generalization is based on a
nonrandom sample of 3 cars)
– example: Of the 19 hijackers on Sept. 11, 15 were
Saudis. I think we can safely conclude that Saudi
Arabia is a breeding ground for terrorists.
inductive and deductive
generalizations
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Deductive Generalization: proceeds from a
general rule or general principle to a specific case
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example: Brazilians love soccer. Hector is from
Brazil, so he probably loves soccer too.
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example: Don’t give money to that vagrant.
They are all winos and drug addicts.
example: Biff is a Republican, so of course he’ll
be opposed to gun control.
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tests of generalizations
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How valid or reliable is the “general rule”?
Is the sample from which the generalization is
drawn random, and representative?
Is the sample from which the generalization is
drawn sufficient? (sample size)
Are there any exceptions to the rule?
Even if the general rule is true, does it apply in
this particular case?
Reasoning by Example
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A sub-set of inductive generalizations (a sample of one,
or a few)
Offers a generalization based on one or more cases to
other cases which are presumed to share the same
features as the example.
Examples may be based on personal experience,
hearsay, anecdotes, or case studies
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example: testimonials on infomercials, “The X47 Super mop
worked so well I threw away all my other mops!”
example: deciding whether to take a class, see a movie, or
eat at a particular restaurant based on a friend’s say so.
reasoning by example: Beware of
testimonials!
These
testimonials
serve as
examples of
how effective
diets,
supplements, or
exercise
equipment is
He is a real person, but
was he selected at
random?
Reasoning by example: Beware of
testimonials!
“Before” and
“After” pictures
for miracle
diets, or
testimonials for
various products
are based on
examples.
tests of examples
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Is the example relevant or germane?
How typical or representative is the example?
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Watch out for hand-picked examples
Do the examples cover a critical period of time?
Are there enough examples to prove the case?
Are there any negative or contradictory examples?