The results of electrical conductivity measurements on SrCe0.95Yb0.05O3 under controlled oxygen partial pressure and temperature are presented. A defect model consistent with experimental results is proposed which provides for p(O2)(-1/4) dependent n-type, P-O2-independent oxygen ion and p(O2)(+1/4) dependent p-type conductivity components. The band gap, reduction, oxidation and ion-migration energies are determined from an analysis of the data in terms of the proposed defect model. These results suggest that some earlier data interpreted in terms of protonic conduction may require re-evaluation.