Lecture 17 Flashcards
(21 cards)
What are the types of errors?
- Constant error
- Absolute error
- Variable error
Define:
Constant error
- Compute the average signed error score
- Provides measure of movement bias (over/undershoot, right/leftward bias etc.)
How is constant error computed?
- Subtract target value from trial value
- Sum up the differences in each trial and divide by number of trials
What is the issue with constant error?
Sometimes give illusion that there is no error
Define:
Absolute error
- Average unsigned error score
- No direction, only considers the magnitude of error
How is absolute error calculated?
- Subtract target value from trial value; take the absolute value
- Sum up the absolute values in each trial and divide by number trials
What is the issue with absolute error?
Does not tell one about a consistent bias (direction) of error
What is variable error also known as?
Standard deviation
How is variable error calculated?
- Use constant error along with variable error
- This allows on to see the consistent bias, and see the actual deviations
What is root mean squared error and how is it calculated?
Looking at difference between performance and criterion at different points in time/space and adding that up, finding the average of that value
How is movement described?
- Qualitative description
- Movement kinematics
How is qualitative description taken?
Verbal descriptions, time-lapse photography
What are the key parts in movement kinematics?
- Displacement
- Velocity
- Acceleration
Define:
Displacement
Spatial position of effector during movement
What is the trademark healthy human movement displacement?
Curved linear movements
Define:
Velocity
Rate of change of an object’s position with respect to time
What is the relationship between displacement and velocity?
Peak velocity linearly increases with movement displacement
What shape is the velocity graph roughly?
Roughly bell shaped, slightly skewed due to necessary precision calculations in movement
Define:
Acceleration
Change in velocity of an object during movement
What is the relationship between peak acceleration and movement displacement?
Peak acceleration will peak with the increase of movement displacement
What can acceleration tell us?
Identifies the smoothness of a movement/trajectory
