TERD – Time-Error-Rate-Diagnosis
This worksheet allows for diagnosis of impairment in tasks that provide a Time score and an Error score. The method considers the pair of scores as a single one (a bivariate score) and extracts diagnostic information from it. An example of a field in which such an analysis would be useful is the diagnosis of developmental dyslexia on grounds of reading tasks.
INPUT What one needs are the raw scores of the standardization sample, expressed in time units and in error counts (the maximum possible number of errors is also required), as well as the raw data from the to-be-assess individual. Age-adjusted scores are also allowed, but with important caveats (see the Instructions file for details).
As an OUTPUT, the Worksheet provides an adjusted version of the Mahalanobis distance, a score that expresses how far the bivariate performance of an individual is from the bivariate mean performance of the standardization sample, as well as a p-value associated to it. A plot is also offered that gives a grasp as to the relative position of a subject’s bivariate score with respect to the scores of the standardization sample; this plot allows one to understand to what extent the deficit is due to a time-related or to an error-rate component.
TERD 1.0 Instructions (as of February, the 22nd, 2018) 
A commentary – in Italian – was recently submitted for publication on this tool:
Toraldo A. (submitted). Diagnosis of dyslexia: a bivariate solution to a bivariate problem. Psicologia Clinica dello Sviluppo.
Toraldo A. (2019). Diagnosi di dislessia: una soluzione bivariata ad un problema bivariato. Un commento a «Indice di Efficienza della Lettura (IEL)», di D'Antuono, Savelli, Stella. Psicologia Clinica dello Sviluppo, 23, 237-246