Well-intentioned people who perform CPR on cardiac-arrest victims get it wrong more often than not, often reducing the victimÕs already razor-thin chances of survival, according to a study published in todayÕs Journal of the American Medical Association. In a study of 2,071 cases of cardiac arrest over a six-month period, Dr. John Gallagher of the Albert Einstein College of Medicine in New York City found that 662 victims were given CPR by bystanders. CPR was performed incorrectly in 357 (or 54%) of the cases. Result: those patients survived at only one-third the rate of those who received correct CPR assistance. "This study is extremely important," reports TIME's Andrea Dorfman. "Anyone skilled in CPR must take the refresher course regularly. Otherwise, they may find themselves in a situation like those described in the Einstein study, where they forget something during the crisis, and actually do more harm than good."