We consider here the problem of scheduling tasks in the imprecise computation model to minimize the maximum error. Given a task system and a schedule of it, the maximum error of the task system is equal to the error of the task that has the largest error when the task system is executed according to the schedule. We describe two preemptive algorithms for scheduling on a processor n dependent tasks with rational ready times, deadlines, and processing times. Each schedule found by our algorithms is an optimal schedule with the minimum total error, and according to this schedule the maximum error is minimized. The run times of our algorithms are O(n3) and O(n2).