How to Lie with Statistics

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How to Lie with Statistics

• Chapters 8-10 Daniel Huff

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Chapter 8 Post-Hoc Rides Again

• If B follows A, then A has caused B
• Perhaps neither of these things has produced the
  other, but both are a product of some third
  factor
• Correlation can actually be of any of several
  types and can be limited to a range
• Given a small sample, you are likely to find some
  substantial correlation between any pair of
  characters or events

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Chapter 8 Post-Hoc rides Again

• A common kind is when the relationship is real
  but it is not possible to be sure which of the
  variables is the cause and which is the effect
• Perhaps there is a real correlation, yet neither
  of the variables has any effect at all on the
  others
• Watch out for a correlation conclusion beyond the
  data which it has been demonstrated. (Ex. More
  rain better crops)

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Chapter 8 Post-Hoc Rides Again

• Negative correlation is a statement that as one
  variable increases the other tends to decrease
  (or visa-versa)
• Positive correlation is a statement that as one
  variable decreases the other tends to increase
  (or visa-versa).

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Chapter 9 How to Statisculate

• Misinforming people by the use of statistical
  material might be called statistical
  manipulation.
• False charts in magazines and newspapers
  frequently sensationalize by exaggeration, rarely
  minimize anything

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Chapter 9 How to Statisculate

• One of the trickiest ways to misrepresent
  statistical data is by means of a map (Ex.
  National income grouping, using the statistical
  average of mean instead of the smaller and more
  informative median, and assumes that income is
  directly proportionate to size.)
• Using decimals as a way to lend improper
  precision to statistics

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Chapter 9 How to Statisculate

• Any percentage figure based on a small number of
  cases is likely to be misleading
• The shifting base -- percentages taken off
  different totals to imply different amounts
• Percentages added together, or mathematically
  used in other ways (Ex. I mix em fifty-fifty
  one horse, one rabbit.)

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Chapter 9 How to Statisculate

• Statistics is as much an art as it is a science
• A great many manipulations and even distortions
  are possible within the bounds of propriety.
  Often the statistician must choose among methods,
  a subjective process, and find the one that
  he/she will use to represent the facts.
• This suggests giving statistical material, the
  facts and figures in newspapers and books,
  magazines and advertising, a very sharp second
  look before accepting any of them.

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Chapter 10 How to Talk Back to a Statistic

• 1st thing to look for is bias
• Conscious bias
• Direct misstatements
• Ambiguous statement
• Selection of favorable data
• Suppression of unfavorable
• Units of measurement may be shifted
• Improper measure (trickery covered by the use of
  the word average)

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Chapter 10 How to Talk Back to a Statistic

• Who says so? How do they know?
• A biased sample, or that has been selected
  improperly or has selected itself
• Reported correlation is it big enough to mean
  anything? Are there enough cases to add up to
  any significance? Look for a measure of
  reliability (sources for error)

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Chapter 10 How to Talk Back to a Statistic

• What is missing?
• Look out for average variety unspecified, a
  matter where mean and median might be expected to
  differ substantially
• Percentages are given and raw figures are missing
• The factor that caused change to occur, implying
  that some other more desired factor is
  responsible (Ex. Looking at total deaths rather
  than death rate, dont forget there are more
  people now than there used to be)

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Chapter 10 How to Talk Back to a Statistic

• Did somebody change the subject?
• Watch out for a switch somewhere between the raw
  figure and the conclusion
• Strange things crop out when figures are based on
  what people say -- even about things that seem to
  be objective facts

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Chapter 10 How to Talk Back to a Statistic

• Does it make sense?
• Often cuts a statistic down to size when the
  whole idea is based on an unproved assumption
• Use common sense
• The trend-to-now may be a fact, but the future
  trend represents no more than an educated guess