Multiple non-defective samples of a DUT are selected. A quiescent power supply current (IDDQ) is measured for each of test vectors which are switched, for each of the non-defective samples. Statistical IDDQ values are measured in increments of the test vectors, and first array data is created including identifiers for the test vectors and the statistical IDDQs as elements. The first array data is sorted using the IDDQ value as a key so as to create second array data. The difference in quiescent power supply current is calculated by making difference between adjacent current elements of the second array data, so as to create third array data including the identifiers for the test vectors and the differences of current value as the elements. The third array data is sorted using the difference in current value as a key, and creates fourth array data.