A new time-independent reliability importance measure

Modern digital systems pose new challenges to reliability analysts. Systems may exhibit a non-coherent behavior and time becomes an important element of the analysis due to aging effects. Measuring the importance of system components in a computationally efficient way becomes essential in system design. Herein, we propose a new importance measure for time-independent reliability analysis. The importance measure is based on the change in mean time to failure caused by the failure (success) of a component. It possesses some attractive properties: i) it is defined for both coherent and non-coherent systems; ii) it has an intuitive probabilistic and also geometric interpretation; iii) it is simple to evaluate. It turns out that the proposed importance measure leads naturally to a test of time consistency. We illustrate the properties with examples of coherent and non-coherent systems. A comparison with the ranking of other time-dependent and time-independent reliability importance measures is also offered. The realistic application to the reliability analysis of an H.264 video decoder concludes the work.