Inductive Reasoning

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Inductive Reasoning

• Statistical Probability

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Inductive Reasoning, defined

• Unlike deductive reasoning, Inductive reasoning
  is not designed to produce mathematical
  certainty, but statistical probability
• the chain of evidence begins with an observation
  and then combines it with the strength of
  previous observations in order to arrive at a
  conclusion.
• Induction begins with specifics

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Inductive Reasoning, example

• Observation John came to class late this
  morning.
• Observation Johns hair was uncombed.
• Prior experience John is very fussy about his
  hair.
• Conclusion John overslept

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Inductive Reasoning, type 1

• Induction by Enumeration, or, more commonly,
  Generalization
• whenever you make a general statement (all
  salesmen are pushy) based on observations with
  specific members of that group (the last three
  that came to my door were pushy)
• also generalize when you make an observation
  about a specific thing based on other specific
  things that belong to the same group (Ed is a
  salesman, so hell probably be pushy.)
• that movement is called an inductive leap.

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Inductive Reasoning, type 2

• Induction by Analogy
• to draw a conclusion about one thing based on its
  similarities to another thing. Ex
• In the 1960's, America was drawn into a war in a
  foreign country, with a harsh terrain largely
  comprised of jungles, against enemies that we
  could not recognize and friends that we could not
  count on. That war began slowly, by sending a few
  "advisors" to help survey the situation and offer
  military advice, and it became the greatest
  military disgrace that our country has ever
  known. We all know what happened in Vietnam. Do
  we really want a repeat performance in Iraq?

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Inductive Reasoning, type 3

• Induction by Statistical Inference
• assuming that something is true of a population
  as a whole because it is true of a certain
  portion of the population
• sample sizes must be large enough to avoid huge
  margins of error must also be randomized