Explanation of performance metrics to characterize psychophysical sampling procedures.

(A) Distribution of threshold estimates for a given template. (B) Distribution of the absolute errors. (C) Percentage within bounds (PCTw/iB) as a function of the tolerance interval. Each point of this function is generated by integrating the area of the absolute error distribution from zero to the respective error, respectively tolerance, value. (D) After a nonlinear transform of the x axis to [0, 1], the normalized area under the curve (nAUC) can be calculated (1 corresponding to perfect estimation for this template). (E) When the nAUC is computed for different templates within a threshold and slope parameter space, the performance can be visualized as a surface in a three-dimensional space. (F) After normalizing the parameter space axes to [0, 1], the normalized volume under the surface (nVUS) can be calculated (1 corresponding to perfect estimation across all templates). Note that the metrics are illustrated for the present application of proprioceptive joint angle assessments using a 2AFC paradigm, for a psychometric function template .