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Simon Fraser University *

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311

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Aerospace Engineering

Date

Oct 30, 2023

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Constant error (CE): What is your directional bias (in one direction)? Measure of how far away from the target and in which direction ( + or -, signed deviation) - Measures accuracy and bias (amount and direction) - Mean CE represents average magnitude and deviation Beware of cancellation effects - this time we are interested in SIGNS and get the constant error 16 - if bias -5 and all in particular error, then variability is low, doing same thing over and over, so consistent, maybe one instruction to overcome variability around your own scores - 2 methods work - interest in deviations from the mean Performance Consistency/Variability - Variable Error (VE) - Measure of how consistent (or, conversely, variable) you were - “Spread” of scores about your own average score (M) - Or...spread of errors around your own average error (CE) - first calculate what own mean value was - then look at deviations from individual score to own mean 18 - be AWARE OF WHAT THE MEASURE DOES 19 - can do with constant error as well - then take each constant error from mean constant error 20 - person b hitting same area consistently 21 - carrie directional bias - gary most accurate, getting same amount of errors, low magnitude of error - gary is most consistent radial error - use pythag 25 - want to know time on target

- what about continuous tasks where goal is to follow a target/stay horizontal? - How accurately and consistently do we maintain our position in a path? 27 - review the recording Measures of Movement Forms Motion is captured by Multiple cameras - Digital video cameras or 3D motion trackers - Markers (usually LEDs) are tracked through space. - Each marker is “sampled” at high rates to give kinematic data These data points undergo a Kinematic Analysis - Displacement - Velocity - Acceleration When something shows change over time (not just end result) we can get kinematics EG: discrete, single dimension reaching action to a target. Displacement = Change in spatial position in one or more dimensions Peak Velocity (PV) corresponds to “0” acceleration. In smooth displacements, PV occurs half - way through the movement Secondary accelerations: Indicative of corrections to original movement REVIEW SLIDE GRAPHS 31 look at velocity and acceleration to see how goal was attained - peak velocity shows index of expertise, how fast they did it - peak velocity point of zero acceleration - acceleration - whether they are using vision to hone in on a target (secondary acceleration) how sensory information is used to control movement Summary - Error measures help to give information about performance on a task (e.g., error in timing, if the goal was to make a movement in 500ms (1/2sec), or error in distance, if the goal was to stop/hit a target (e.g., putting). - One error measure can also capture 2 dimensions, such as radial error, which is useful when considering aiming tasks such as target - shooting. - We can also describe HOW a movement was completed if we know how movement changed over time. For example, this might be change in the end-point of a limb (foot, when hurdling or hand when making pointing movements). This is referred to as movement kinematics. We are typically interested in measures of velocity (speed) and accelerations. The smoothness of the movement profile gives us an indication of how the movement was completed and how it might have been prepared (which we explore later in the

course). CE - chester intended to overthrow the 50ft target by only 0.4ft, john lee tended to underthrow the target by 2.6ft AE - chester was off target more than john lee VE - even though chest’s average throw was closer to the goal than john lee, chester was more inconsistent in the throws - measures tendency absolute constant error traits magnitude of average deviation but presents two score from cancelling out when data from more than one person average together to present group score continuous tracking tasks - root mean square error - computing distance of person’s tracking behaviour from target line at preset distance points along track - constant interval alone track - first calculate squared deviation for each measured position along track, then take square root of the sum of those scores - reflects bias tendency and inconsistency

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