Former U.S. Vice President Dick Cheney received a lot of publicity after his fourth heart attack. A portable defibrillator was surgically implanted in his chest to deliver an electric shock to re- store his heart rhythm whenever another attack was threatening. Researchers at the University of Rochester (NY) Medical Center implanted defibrillators in 742 patients after a heart attack and compared them with 490 similar patients without the implant. Over the next 2 years, 98 of those without defibrillators had died, compared with 104 of those with defibrillators.
(a) State the hypotheses for a one-tailed test to see if the defibrillators reduced the death rate.
(b) Obtain a test statistic and p-value.
(c) Is normality assured?
(d) Why might such devices not be widely implanted in heart attack patients?