Eddy current inspection is widely used in nondestructive evaluation to detect cracks in metal structures. The impedance plane measurement response collected using our motion controlled eddy current inspection system, are used in the analysis. A scalar reduction from the impedance plane response is used to minimize human-factor variation. We apply a noise interference model to the data from a large-scale experiment taking measurements on fastener rivet holes in multi-layer structures with fatigue cracks, and estimate the probability of detection (POD). The estimates of POD as a function of crack size will be valuable for future model-assisted POD study.