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1. Logical Fallacies: Overgeneralizing

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3. The Overgeneralizing Fallacy
A Common Core Lesson
By
Dean Berry, Ed. D.
Gregg Berry, B. A.
Common Core Curriculum Solutions
www.commoncorecurriculum.info

4. Reading with Your Eyes and Your Brain
Skillful readers learn how to read persuasive or
opinionated text with a very critical eye. They
realize that the author’s purpose is to convince the
reader to believe what the author is saying and to
consider the arguments given as valid even if they
violate logical reasoning and lack supporting
evidence. The author’s motive may be to get the
reader to buy something, vote a certain way,
change an attitude, or behave differently.

5. • In order to avoid manipulation by the author,
good readers learn how to detect poor
reasoning and faulty arguments. They are
able to identify the various logical fallacies
such as begging the question, strawman,
overgeneralization, slippery slope, and
others. During this lesson, we will study
logical fallacies.

6. If I can’t see you, you can’t see me!

7. Is this logical reasoning?

8. Who’s argument is based on logic?

9. Your reasoning must result
in a logical conclusion.

10. Does the order of events always
determine the cause of events?
Fallacy: After This Therefore
Because of This
When you're wondering why something
happened, it's reasonable to assume
that the cause came before the event.
It's less reasonable, however, to
suppose that ANY circumstance
preceding an event must have helped to
cause that event. The fact that A
occurred and then B occurred doesn't
necessarily mean that A caused B.

11. This is the essence of the After This Therefore Because of
This Fallacy. The first event must have caused a second
event simply because the first event came right before it.
It appears whenever someone argues that, they assume
that the first event actually caused the second event.

12. Logical Fallacies

13. Faulty Generalization
There are many ways in which the relationship between
generalizations and specific instances can be abused. One
of the more common ones is to over-generalize from an
unrepresentative group.

14. For example:
The overwhelming majority of my friends are liberals who support higher
taxes on the wealthy. So, any politician who is a liberal and supports this
issue is very likely to get elected.
I live in New York City and associate mostly with people who have
political views similar to my own. It's wrong for me to generalize from
the highly unrepresentative sample of my friends to voters
everywhere in the country.

15. Sweeping Generalizations

16. The Overgeneralization Fallacy
Overgeneralization is the use of small
and/or non-representative samples of real
data to make an inference that is incorrect.
It is considered a cognitive bias, a logical
fallacy, and a misuse of statistics.
Why you should do
what I want you to

17. Sample Size is Critical When Generalizing
When research surveys are conducted by social
scientists, they use statistical methods to measure the
reliability of their sampling. Most national surveys use a
random sample of from 1200 people to 2000 people. The
larger the number of people in the survey, the more
accurate the survey will be. With a large enough sample
of the population being surveyed, scientists can predict
the attitudes or beliefs of a much larger population such
as a state or country with an error rate as low as 3 or 4
percent. However, scientists have to make sure that the
characteristics(gender, age, location, etc.) in the random
sample are representative of the larger population to
which the generalization is applied.

18. Non-representative Samples
What is wrong with this conclusion?
There have been a number of scandals
involving financial firms committing fraud.
You can’t trust any of these big financial
firms.
These big financial firms and workers are
thieves stealing money from society.

19. Is this an overgeneralizing fallacy?
Why? Why Not?
This week we have read about elected officials in
five different cities who are either under
investigation for corruption in office or have
already been convicted of malfeasance in office. It
seems that all politicians are crooks and we
should throw the bums out.

20. Pair Share
Turn to your neighbor and discuss
your answer to these questions.
Is this statement an example of the over generalizing fallacy?
This week we have read about elected officials in five
different cities who are either under investigation for
corruption in office or have already been convicted of
malfeasance in office. It seems that all politicians are
crooks and we should throw the bums out.

21. Is this an example of the
overgeneralizing fallacy?
Three senior citizens died after receiving swine flu
vaccine in 1976. Therefore, it seems vaccines are
bad for you and people should not use them.

22. Pair Share
Turn to your neighbor and discuss
your answer to these questions.
Is this statement an example of the over generalizing fallacy?
Three senior citizens died after receiving swine
flu vaccine in 1976. Therefore, it seems
vaccines are bad for you and people should
not use them.

23. Is this an example of the
overgeneralizing fallacy?
An analysis of testing results places
American high school students below
most students in industrialized
countries. Apparently, American high
schools students are less educated than
most European students.

24. Pair Share
Turn to your neighbor and discuss
your answer to these questions.
Is this statement an example of the over generalizing fallacy?
An analysis of testing results places
American high school students below most
students in industrialized countries.
Apparently, American high schools students
are less educated than most European
students.

25. Is this argument using the
overgeneralization fallacy?
The governor and two state legislators in Illinois
were arrested and convicted of political corruption.
Therefore, it is fair to say that most of the politicians
in Illinois are corrupt and should be investigated.

26. Pair Share
Turn to your neighbor and discuss
your answer to these questions.
Is this statement an example of the over generalizing fallacy?
The governor and two state legislators in Illinois
were arrested and convicted of political corruption.
Therefore, it is fair to say that most of the politicians
in Illinois are corrupt and should be investigated.

27. Is this an example of the
overgeneralizing fallacy?
Smaller mid western and southern
states have more undeveloped and rural
areas. People living in rural farming
areas have a large number of guns per
person that they use for protection and
hunting. As a result, people living in
small rural states prefer gun rights over
gun control by a large margin.

28. Pair Share
Turn to your neighbor and discuss
your answer to these questions.
Is this statement an example of the over generalizing fallacy?
Smaller mid western and southern states have
more undeveloped and rural areas. People living
in rural farming areas have a large number of
guns per person that they use for protection and
hunting. As a result, people living in small rural
states prefer gun rights over gun control by a
large margin.

29. Are these examples of
over generalizing?
• Professional basketball players are much taller than the
general population. Therefore, tall people will be better
basketball players than short people.
• Spending a lot of time in the sun leads to skin cancer.
So beach goers will develop cancer in the future.
• Fast drivers have fatal accidents. Therefore, slowing
down will save lives.
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30. Pair Share
Turn to your neighbor and discuss
your answer to these questions.
Are these statements examples of the over generalizing fallacy?
Professional basketball players are much taller than the
general population. Therefore, tall people will be better
basketball players than short people.
Spending a lot of time in the sun leads to skin cancer. So
beach goers will develop cancer in the future.
Fast drivers have many fatal accidents. Therefore, slowing

31. Did you hear about the teenagers who
vandalized the park? I did! Teenagers
are so irresponsible and destructive.
Is this an over generalizing fallacy?

32. Pair Share
Turn to your neighbor and discuss
your answer to these questions.
Is this statement an example of the over generalizing fallacy?
Did you hear about the teenagers who
vandalized the park? I did! Teenagers are
so irresponsible and destructive.

33. Quick Write
Think about one of the issues listed below and write an argument that uses the
over generalization fallacy to convince people that the following idea
includes everybody.
• Going to college
• Increasing the driving age for teenagers
• Selecting a dog or a cat as a pet
• Getting good grades
Remember to make a sweeping statement that includes
all members of the group regardless of evidence.