Outcome variables
The variables were CPR quality components, as follows: first, compression depth (50 to 60 mm was expected as the correct value); second, compression rate (the number of chest compressions in 1 minute; the expected correct frequency was 100 to 120 compressions per minute); third, the time of correct frequency (the percentage of time throughout the whole CPR session when the frequency was within 100–120 compressions/min; a percentage of 95%–100% was considered successful); and fourth, the time of correct chest release (the percentage of time throughout the whole CPR session when the chest was being correctly released; 95%–100% was considered successful.