Cyber-physical systems are differentiated from other real-time embedded systems based on the tight intertwining of the cyber infrastructure with the physical components upon which it exerts control. This close interaction manifests as interdependence in operation and failure. This paper aims to determine and quantify the type and extent of dependency in a cyber-physical system using a method inspired by the analytic network process. The method incorporates several steps, namely, identification of failures sequences, and graph-theoretical representation of functional dependencies between components, and finally, calculating dependency indices. We illustrate the proposed approach through application to the IEEE 14-bus power system.