This paper presents a sensitivity analysis for the dimensioning of real-time systems in which sporadic tasks are executed according to the preemptive Earliest Deadline First (EDF) scheduling policy. The timeliness constraints of the tasks are expressed in terms of late termination deadlines. A general case is considered, where the task deadlines are independent of the task sporadicity intervals (also called periods). New results for EDF are shown, which enable us to determine the C-space feasibility domain, such that any task set with its worstcase execution times in the C-space domain is feasible with EDF. We show that the C-space domain is convex, a property that can be used to reduce the number of inequalities characterizing the C-space domain.