Abstract

The problem of how developmental dyslexia should be diagnosed on grounds of both speed and accuracy of reading performance can be solved by focusing on the bivariate nature of the problem, as an alternative to using aggregate scores that combine both measures but whose theoretical/pragmatical meaning is uncertain. The TERD worksheet, available online, provides the Mahalanobis distance, an absolute and continuous bivariate measure that informs about how far the assessed subject is from the normative sample taking speed, accuracy, and their correlation into account, and also provides a p-value that can be used in diagnosis. TERD is very simple to use and does not require any manual computation - it just requires the user to insert raw (or adequately adjusted) scores in a table.