Question

4. Swor et al. (A-9) looked at the effectiveness of cardiopul- monary resuscitation (CPR) training in people over 55 years old. They compared the skill retention rates of subjects in this age group who completed a course in traditional CPR instruction with those who received chest-compression only cardiopulmonary resuscitation (CC-CPR). Independent groups were tested 3 months after training. The table below shows the skill retention numbers in regard to overall com- petence as assessed by video ratings done by two video evaluators.

Answer 1

Probability of an event= Total no of favorable outcomes/Total no of outcomes

a) 1. Probability that a randomly selected person was enrolled in CC-CPR class = total people in CC-CPR class/total sample = 29/56 = 0.5179

2. Probability that a randomly selected person was rated competent= total people rated competent/total sample = 27/56 = 0.4821

3. Required probability = P(Yes or CC-CPR) = P(Yes) + P(CC-CPR) - P(CC-CPR and Yes) = (27+29-15)/56 = 0.7321

4. P(Yes|CC-CPR) = P(yes and CC-CPR)/P(CC-CPR) = 15/29 = 0.5172