EXAMPLE 7 Do medical helicopters save lives?

Accident victims are sometimes taken by helicopter from the accident scene to a hospital. Helicopters save time. Do they also save lives? Let’s compare the percentages of accident victims who die with helicopter evacuation and with the usual transport to a hospital by road. The numbers here are hypothetical, but they illustrate a phenomenon that often appears in real data.

We see that 32% (64 out of 200) of helicopter patients died, but only 24% (260 out of 1100) of the others died. That seems discouraging.