In nondestructive inspection of a part, the accept / reject decision is typically based on the comparison of the measured variable to a threshold value. In a practical test situation various factors introduce randomness and uncertainty in the measurement, thus affecting the accept / reject decision. The concept of probability of detection offers a measure of the capability of nondestructive evaluation methods to detect defects, in the presence of different sources of uncertainties. For instance, it has been previously established [1], that mechanical stress introduces variations in the magnetic flux leakage measurements. Residual stress affects the magnetic properties of ferromagnetic materials and is one of the factor s that can potentially affect the detectability of defects.