Abstract: A method for determining the integrated circuit manufacturing operations that are the principle contributors to defect limited test yield loss comprises extracting the electrical faults for the important range of defect sizes from the layout data base; determining the signatures of the electrical response of faulted circuits to the input test stimuli; determining the statistical frequency distribution of the signatures for a fixed ratio of defect densities on the several process layers; determining the frequency distribution of the signatures observed in testing a wafer or group of wafers; and adjusting the defect densities amongst the process layers to minimize the difference between the predicted and observed frequency distributions such that the adjusted defect distribution provides a measure of the relative contribution of the process layers to yield loss.