Error Measures

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Error Measures

• Emily Wughalter, Ed.D.

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Error Measures

• Error measures help provide detail about
  performance when meeting an object in space.
  They help to quantify performance.
• As in swinging a bat and meeting a ball in space
  with the end of a bat
• As in wanting to click on an icon by moving
  cursor on the screen
• As in grabbing a stick of deodorant from the
  medicine cabinet
• As in hitting a golf ball off a T, or in hitting
  the golf ball so that it is precisely directed in
  its flight and for its landing location
• As in driving a car and being able to drive in a
  lane with acceptable variability

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Measuring Error

• Error measures are determined to explain various
  phenomena and by applying varying algorithms.
  They can be used to explain performance for a
  series of trials (trial blocks) with regard to
  matching a moving or stationary object in space.
• Consider validity
• Consider ecological validity
• Consider reliability
• Consider objectivity
• Consider assumptions
• Consider practical value and need

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Error Measures in Motor Learning

• Constant error
• Variable error
• Absolute error

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Constant Error (CE)

• CE provides information about a performers
  response bias
• Does the performer generally respond early
  (undershoot) or late (overshoot) with respect to
  the target or matching location of a movement?
• Does the performer have a general tendency?
• CE is determined by adding up the algebraic error
  scores and dividing by the number of scores or
  calculating the mean.
• CE should be presented with VE to more fully
  understand its meaning.

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Variable Error (VE)

• VE helps to explain the variability (changes) in
  performance across a series of trials between a
  position in space and the matching of that
  position.
• Calculate VE as the standard deviation of a set
  of scores (trial block)

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Absolute Error

• AE measures the average difference or average
  total error between the target location and the
  matching performance across a series of trials.
• Calculate absolute error by obtaining the mean of
  the absolute value of the algebraic error scores
  for a series of trials.