A controversial new device, the implantable cardiac defibrillator (ICD), was used in a clinical trial to determine if it improved survival for heart-attack patients over the standard drug treatment. The trial provided the following information: Two years after the first heart attack, 85 percent of the ICD patients were still alive, compared to 70 percent of the drug treatment group. No additional data were available after the 24-month trial.

a. What is your best guess on survival probability after the trial is over?

b. Calculate the improvement in life expectancy during the trial. What is your best estimate of improved life expectancy after the trial?

c. Graph the mortality function for both the ICD group and the drug-therapy group.

d. What is the difference in life expectancy between the two groups?