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  • False Conversion
  • False Dilemma
  • False Effect
  • Far-Fetched Hypothesis
  • Faulty Comparison
  • Gambler’s Fallacy
  • Genetic Fallacy
  • Hasty Generalization
  • Having Your Cake
  • Hedging
  • Historian’s Fallacy
  • Homunculus Fallacy
  • Hypnotic Bait and Switch
  • Hypothesis Contrary to Fact
  • The Fallacies: If–Mu
  • If-By-Whiskey
  • Illicit Contraposition
  • Illicit Major
  • Illicit Minor
  • Illicit Substitution of Identicals
  • Inconsistency
  • Inflation of Conflict
  • Jumping to Conclusions
  • Just Because Fallacy*
  • Just In Case Fallacy
  • Least Plausible Hypothesis
  • Limited Depth
  • Limited Scope
  • Logic Chopping
  • Ludic Fallacy
  • Lying with Statistics
  • Magical Thinking
  • Meaningless Question
  • Misleading Vividness
  • Missing Data Fallacy*
  • Modal (Scope) Fallacy
  • Moralistic Fallacy
  • Moving the Goalposts
  • Multiple Comparisons Fallacy
  • The Fallacies: Na–Ri
  • Naturalistic Fallacy
  • Negating Antecedent and Consequent
  • Negative Conclusion from Affirmative Premises
  • Nirvana Fallacy
  • No True Scotsman
  • Non Sequitur
  • Notable Effort
  • Overwhelming Exception
  • Package-Deal Fallacy
  • Poisoning the Well
  • Political Correctness Fallacy
  • Post-Designation
  • Prejudicial Language
  • Proof by Intimidation
  • Proving Non-Existence
  • Quantifier-Shift Fallacy
  • Quantum Physics Fallacy*
  • Questionable Cause
  • Rationalization
  • Red Herring
  • Reductio ad Absurdum
  • Reductio ad Hitlerum
  • Regression Fallacy
  • Reification
  • Relative Privation
  • Retrogressive Causation
  • Rights To Ought Fallacy*
  • The Fallacies: Sc–Wi
  • Scapegoating
  • Selective Attention
  • Self-Sealing Argument
  • Shoehorning
  • Slippery Slope
  • Special Pleading
  • Spiritual Fallacy*
  • Spotlight Fallacy
  • Statement of Conversion
  • Stereotyping
  • Stolen Concept Fallacy
  • Strawman Fallacy
  • Style Over Substance
  • Subjectivist Fallacy
  • Subverted Support
  • Sunk-Cost Fallacy
  • Suppressed Correlative
  • Texas Sharpshooter Fallacy
  • Tokenism
  • Two Wrongs Make a Right
  • Unfalsifiability
  • Unwarranted Contrast
  • Use-Mention Error
  • Weak Analogy
  • Willed Ignorance
  • Wishful Thinking
  • Base Rate Fallacy

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    (also known as: neglecting base rates, base rate neglect, base rate bias [form of], prosecutor's fallacy [form of])

    Description: Ignoring statistical information in favor of using irrelevant information, that one incorrectly believes to be relevant, to make a judgment.  This usually stems from the irrational belief that statistics don’t apply in a situation, for one reason or another when, in fact, they do.

    Example #1:

    Only 6% of applicants make it into this school, but my son is brilliant!  They are certainly going to accept him!

    Explanation: Statistically speaking, there is a 6% chance they will accept him.  The school is for brilliant kids, so the fact that her son is brilliant is a necessary condition to be part of the 6% who do make it.

    Example #2:

    Faith healing works, but not all the time, especially when one’s faith is not strong enough (as generally indicated by the size of one’s financial offering).  Unbiased, empirical tests, demonstrate that a small but noticeable percentage of people are cured of “incurable” diseases such as cancer.

    Explanation: This is true.  However, what is not mentioned in the above is the number of cases of cancer that just go away without any kind of faith healing, in other words, the base rate of cancer remission.  It is a statistical necessity that among those with cancer, there will be a percentage with spontaneous remission.  If that percentage is the same as the faith-healing group, then that is what is to be expected, and no magic or divine healing is taking place.  The following is from the American Cancer Society:

    Available scientific evidence does not support claims that faith healing can cure cancer or any other disease. Some scientists suggest that the number of people who attribute their cure to faith healing is lower than the number predicted by calculations based on the historical percentage of spontaneous remissions seen among people with cancer. However, faith healing may promote peace of mind, reduce stress, relieve pain and anxiety, and strengthen the will to live.[1]

    Exception: If there are factors that increase one’s odds and alter the known statistical probabilities, it would be a reasonable assumption, as long as the variations from the statistical norm are inline with the factors that cause the variation.  In other words, perhaps the mother in our first example knows that her son is gifted musically, that counts for something, then it is not unreasonable to expect a better than 6% probability -- but assuming a 50%, 80%, or 100% probability, is still committing the fallacy.

    Tip: Take some time in your life to read a book or take a course on probability.  Probability affects our lives in so many ways that having a good understanding of it will continually pay off.





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