  We report on resistivity and Hall measurements in thin films of the
electron-doped superconducting cuprate Pr$_{2-x}$Ce$_{x}$CuO$_{4\pm\delta}$.
Comparisons between x = 0.17 samples subjected to either ion-irradiation or
oxygenation demonstrate that changing the oxygen content has two separable
effects: 1) a doping effect similar to that of cerium, and 2) a disorder
effect. These results are consistent with prior speculations that apical oxygen
removal is necessary to achieve superconductivity in this compound.
