Statistical evidence that a diagnostic instrument measures what it is supposed to measure.
Example: SAT performance has been shown to correlate fairly well with one’s college GPA; therefore, the SAT is an empirically valid measure of academic aptitude.
Grinnell, R. (2008). Empirical Validity. Psych Central. Retrieved on June 2, 2015, from http://psychcentral.com/encyclopedia/2008/empirical-validity/