1. Error Measures Emily Wughalter, Ed.D.

2. 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

3. 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

4. Error Measures in Motor Learning  Constant error  Variable error  Absolute error

5. Constant Error (CE)  CE provides information about a performer’s 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.

6. 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)

7. 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.