This paper investigates the impact of the changes of the characteristic polynomials and initial loadings, on behaviour of aliasing errors of parallel signature analyzer (Multi-Input Shift Register), used in an LFSR based digital circuit testing technique. The investigation is carried-out through an extensive simulation study of the effectiveness of the LFSR based digital circuit testing technique. The results of the study show that when the identical characteristic polynomials of order n are used in both pseudo-random test-pattern generator, as well as in Multi-Input Shift Register (MISR) signature analyzer (parallel type) then the probability of aliasing errors remains unchanged due to the changes in the initial loadings of the pseudo-random test-pattern generator.