Lecture 3a, Measurement of Motor Performance (2)

Question 1

Outcome Accuracy: Error Measures

Answer 1

one way to measure performance outcome is via an error score
measures provide information about results of performance, tell us about:
- performance accuracy
- performance bias
- performance consistency
(error scores can give us information about pure accuracy)

Question 2

Absolute Error (AE)

Answer 2

how far a person was from the goal (always positive)
- absolute value of error score (no + or - sign) - ignore signs and just combine all numbers together
- mean AE = mean error score for person across series of trials

AE calculates in just one dimension: x or y (interested in describing performance in one dimension)
how much error in horizontal distance? OR how much error in vertical distance/height?
T = target
*bars just mean take the +ve value
AE = ∑ I xi - T I / n

Question 3

Constant Error (CE)

Answer 3

what is a person’s directional bias (positive or negative)
- measure of how far away from the target and which direction
- mean CE = represents average magnitude and deviation / bias

CE calculated in just one dimension: x or y
how much & direction of error in horizontal? OR how much error & direction in vertical?
T = target
beware cancellation effects!
CE = ∑ (xi - T) / n
* constant error is pretty much the same except we keep the sign in

Question 4

Variable Error (VE)

Answer 4

what is a person’s consistency/variability (spread/SD)
- “spread of scores on your own average score (M)
- or…spread of errors around your own average error (CE)
VE calculated in just one dimension: x or y
how much variability in scores in horizontal direction? OR how much variability in scores in vertical dimension?
*note this is the calculation for standard deviation (SD)

Question 5

Radial Error (RE)

Answer 5

radial distance from the target (always positive)
- absolute value or error score (no + or - sign)
- mean RE = mean error score for person across series of trials
can calculate directly (with measurement stick) or from x and y values (creating triangle with stick)
RE = square root of x2 + y2

Question 6

3 types of Kinematic measures that tell us about how a movement was performed

Answer 6

movement kinematics: displacement, velocity and acceleration

Question 7

Displacement

Answer 7

change in spatial position in one or more dimensions over time…how “far”? (e.g., 120mm)

Question 8

Velocity

Answer 8

rate of change in spatial position in one or more dimensions over time…how “fast”?(e.g., 120mm/s)

Question 9

Acceleration

Answer 9

change in velocity in one or more dimensions over time…how quickly are you speeding up or slowing down… how “jerky or smooth/efficient”? (e.g., 120mm/s/s)