While SSTA seems to embrace more and more advanced statistical techniques, in this paper, with the help of conditional moments, we propose a simple path-based timing approach, which permits us to consider effects of structure correlations, input slope variations and output load variations. This purpose makes us give up the traditional way to characterize cells timing, but take a new attempt: lognormal distribution based model as input signal and active load instead of capacitive load. Numerical results are presented to compare impacts of diverse factors on estimation of path delay distribution.