2_Unit1.2_Measurement copy

28 points 60 hit xi initial absolute error ae the

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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 Xi-T 11-10 9-10 9.5-10 = 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 = (x-axis error)2 + (y-axis 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 bias---a 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 bias--or 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 Xi-T 11-10 9-10 9.5-10 = 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 ∑ (x-m)2 Std Dev = n-1 •  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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