3.30 The paper "Lessons from Pacemaker Implantations" (Journal of the American Medical Association [1965]: 231-232) gave the results of a study that followed 89 heart patients who had received electronic pacemakers. The time (in months) to the first electrical malfunction of the pacemaker was recorded:
ii. What is the approximate time at which only about 10% of the pacemakers initially implanted were still functioning?