This study determined the upper limits of accuracy and consistency of linear and angular measures obtained using the Ariel Performance Analysis System. Reference standards included a meter stick and a universal 360 deg goniometer. Average mean error observed for reconstruction of absolute point estimates was found to be less than 3.5mm. Computer-assisted motion analysis is a method of evaluating human kinematics that offers promise in both research and clinical applications. Because this is a relatively new technology, validation of measurement is fundamental to its use in these areas.
Validity is a complex concept.
Although measurement validity is context-specific, the definition of the upper limits of accuracy of a particular measurement instrument provides the researcher or clinician with critical information to assist in making judgments regarding the degree to which inferences can be drawn from measurement data. Parameters of interest have included absolute and relative point estimations, linear, and angular estimations, consistency of measurement throughout a defined data acquisition region, the ability of a system to track a moving object, and estimations of linkage dynamics. Haggard and Wing 4 studied the accuracy of the Northern Digital's Watsmart optical tracking system applied to linear measurements. The context of their assessment was a reaching activity, and their study included reconstruction and quantitative measures of accuracy. A data acquisition region of 66cm by 66cm in the horizontal or xy-plane was defined.