Electron mobilities have been measured in 1,1’-dioxo-2-(4-methylphenyl)-6-phenyl-4-(dicyanomethylidene)thiopyran (PTS) doped poly(styrene) (PS) over a range of fields, temperatures, and PTS concentrations. The results are described by a formalism based on disorder, due to Bassler and coworkers. The key parameter of the formalism is the energy width of the hopping sites. For PTS-doped PS, the width is approximately 0.129 eV and independent of the PTS concentration. The width is described by a model based on dipolar disorder. The model assumes the width is determined by a dipolar component due to the PTS dopant molecule and a van der Waals component. Agreement with experiment requires that the van der Waals component be dependent on the PTS concentration, increasing with increasing PTS dilution.