Simultaneous Extraction of Spin-Depedent and Spin-Averaged PDFs at high x

We present a new global QCD analysis of inclusive unpolarized and polarized DIS data, using a Monte Carlo approach to simultaneously extract both the spin-averaged and spin-dependent PDFs. We focus on the high-$x$, low-$W$ region, where effects from power corrections, such as target mass corrections (TMCs) and higher twists, are particularly important. We quantify the effects on the extracted PDFs from various theoretical treatments of the power corrections and cuts on the experimental kinematics.