Unformatted text preview: hit 4 it can be argued either way….. 28 points
60% hit xi= initial Absolute Error (AE)
The absolute difference in relevant units between the criterion
and the performance outcome T= target abs (xi – T)
Absolute Error (AE) describes the error along a single dimension We take multiple trials to gain a representative
measure of performance…the average. know this formula fro this exam!!!!!!!!!!!!!!!! Where: AE = ∑ abs (xi – T)
n • ∑ = the sum of
• T = target
• n = number of trials konw how to do this calculation for the exam!!!1 dimension!!!! Absolute Error (AE)
Trial
1
2
3 Xi
11
9
9.5 Abs XiT
1110
910
9.510 =
1
1
0.5 Σ" 2.5
Target
x2 AE = 0.833 0 AE = 9 x3 ∑ abs (Xi – T)
n 10 Then divide by “n”
x1
the number of trials 11 4 RE= is for 2 dimensions!!!!!!! Radial Error (RE)
• Absolute error for two dimensional tasks RE = Errorx2 + Errory2 basically pathagorean theorem What skill might this be appropriate for? Radial Error (RE)
Y axis RE = Errorx2 + Errory2
c b Pythagorean Theorem
a c= X axis Target c2 = a2 + b2
a2 + b2 RE = Errorx2 + Errory2 Radial Error (RE)
Point Xaxis a
b
c
d 3
3
1
2 3
1
3
2 Y axis Yaxis a b X axis d
c 5 another example!!!!! know how to do this calculation on the exam!!!!
RE = (xaxis error)2 + (yaxis error)2 Point Xaxis Yaxis X2 Y2 X2+Y2 a
b
c
d 3
3
1
2 3
1
3
2 9
9
1
4 9 18
1 10
9 10
48
∑
/n it gives a radius of a circle on average how far you are away from the target sqrt 4.24
3.16
3.16
2.83
13.39
3.35 Average RE biasa weighted type of error it falls consistantly on one side or another. Bias in Performance Outcomes
• Absolute measures of accuracy may hold insufficient
information. For example, they fail describe tendencies to
over or under shoot.
• Constant error (CE): represents magnitude of error in a
specific direction (i.e., it is no longer absolute).
CE = ∑ (xi – T) what if someone throws all the horse shoes above their target and
the other person throws them top short but their AE= 1.8. Target
Error 0 AE does not take into account their biasor tendency to under or overshoot. 10 ft AE = ∑ abs (xi – T) … “you missed by that much”
Vs. CE = ∑ (xi – T) … “you overshot by that much” measure of consistency. Constant Error (CE)
Trial
1
2
3 Xi
11
9
9.5 XiT
1110
910
9.510 =
1
1
0.5 Then divide by “n”
the number of trials Σ" 0.5
Target
x
CE = 0.167 2 x3 x1 0 9 CE = 10 11 ∑ (Xi – T)
n 6 he Variability in Performance Outcomes
• Variability is a measure of consistency in performance. The
typical measure is the standard deviation (Std Dev). STD dev!! a measure of consistancy!!!! Where:
∑ = the sum of
x = the individual score
m = the mean
n = the sample size ∑ (xm)2
Std Dev =
n1 • Variable error (VE) is an index of how much variability
there is in the accuracy of performance. m= mean ignores the target and puts the deviation around your own mean!!!!!
know this shit!!!!! Variable Error (Std Dev) Std Dev =...
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 Fall '08
 marcio
 Reaction, Motor control, std dev, variable error

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