[en] This paper introduces a method which uses field or production data rather than specimen data for estimating the probability of rejecting a part containing an imperfection of a given size and for estimating the dependence of this probability upon the nondestructive inspection (NDI) level or levels. In this method the imperfection response features used to make the accept/reject decision are identified for the inspection process of interest. The correlations between the NDI signal characteristics used in making the accept/reject decision, and the relative size (severity) of the imperfection are estimated from destructive examination of material units containing selected imperfection response amplitudes. The destructive evaluation of several retired steam turbine rotors to characterize imperfections located using prototypical field NDI techniques is presently under way as part of EPRI Contract RP502. This method has a distinct advantage over using flawed specimens, both because of possible cost savings and because the uncertainty associated with how well the imperfections fabricated in specimens represent actual imperfections encountered in practice does not enter the analysis method