Comments on "The Confounding Effect of Class Size on the Validity of Object-Oriented Metrics"

It has been proposed that size should be taken into account as a confounding variable when validating object-oriented metrics. We take issue with this perspective since the ability to measure size does not temporally precede the ability to measure many of the object-oriented metrics that have been proposed. Hence, the condition that a confounding variable must occur causally prior to another explanatory variable is not met. In addition, when specifying multivariate models of defects that incorporate objectoriented metrics, entering size as an explanatory variable may result in misspecifed models that lack internal consistency. Examples are given where this misspecification occurs.