On ranking of system components with respect to different improvement actions

For a system consisting of a number of components, an effort should in first hand be given to the most important components. However, this usually depends on which improvement action is offered. Some ranking methods of system components are introduced. We suggest to use different rankings for different improvement actions. Also we give a simple example where these rankings differ considerably. It is indicated that the importance measure suggested by Birnbaum can not be directly used, but our new measure is strongly connected to it. © 1989.