Which Variable to Choose

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Which Variable to Choose

• By Sian Jones

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• Start with a question of causation.
• Does A cause B?
• A is the independent variable
• B is the dependent variable

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• Then you have to ask if A is the only variable
  responsible for the result B.
• What other variables could be involved?
• Could there be a spurious relationship?

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• Spurious relationships
• When the result B is caused by a variable other
  than the independent variable(s) we have observed
  or measured.

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Example The Pledge of Allegiance In 2000 the
Virginia state legislature introduced a law that
would have made it mandatory for public school
students to say the pledge of allegiance every
day. The theory was that the waning patriotism
of the countrys youth was caused by the fact
that traditional manifestations of patriotism
(the pledge and songs like America the
Beautiful) were no longer required in school.
Many in the state protested the law, claiming
that it would be useless, and it was never
enacted.
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• The opponents of the law pointed to the idea
  that, though not saying the pledge corresponded
  with low levels of patriotism, it was not the
  cause. They claimed that Americans in general
  had become less patriotic given the absence a
  major war and the open nature of the world
  community. As patriotism declined, so did its
  overt manifestations i.e. students reciting the
  Pledge of Allegiance.

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• Another question to ask when deciding which
  variables to look at is what kinds of groups the
  subject fits into
• Gender?
• Race?
• Class?
• Then look at the characteristics of those groups
  that could have contributed to the result B.

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Example Crack Babies In the mid 1980s when the
use of crack cocaine was on the rise, researchers
began to predict that the children of women who
used crack during their pregnancies would suffer
from developmental and behavioral problems that
would cost the government billions of dollars to
deal with. As time progressed, however, the
increase in children exhibiting these symptoms
did not increase dramatically.
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• What did they overlook?
• When the researchers re-examined the situation
  they found that most of the women who had had
  crack babies were also members of the lower
  class. As a result, their children were affected
  by the same sorts of things as those of other
  lower-class women such as poor prenatal care,
  malnutrition, neglect, and abuse. All of these
  factors can contribute to the types of problems
  observed in crack-children and, as it turned
  out, were more responsible than the drugs
  themselves.

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• Lessons?
• Dont just stop at the obvious. Ask what
  variables other than the most noticeable ones
  could be responsible for the effects that you
  observe.