To give another perspective on Octavius' question, I've been a paramedic for 15 years and in my experience, I find people's general knowledge of what to do in an emergency very poor. Most people either do nothing, or use common sense; but very few actual have the knowledge or understanding to do the right thing. It's usually the most serious situations that are problematic, heart attacks, strokes, cardiac arrests, unconscious, fits and serious trauma. I've arrived on scene and found bystanders watch people die because they didn't know what to do. It's the resulting sense of helplessness that really affects these individuals. You're fortunate if an ambulance arrives within 10-15 minutes, but it is often these first few minutes that determine the outcome. Someone in cardiac arrest without bystander CPR stands almost no chance of survival after about 5-6 minutes.
As you can guess, I'm an advocate for regular first aid courses and refreshers.