No real error rates though, as I said, it is easy to imagine none occurred in just 28k operations. What if the error rate was (in extremis) 1 death in 50k for

No real error rates though, as I said, it is easy to imagine none occurred in just 28k operations. What if the error rate was (in extremis) 1 death in 50k for non assisted and 1 death in 500k for assisted. The extra cost might be justified on that basis.