10x difference between error rates? No, this is not the case. Well, it might be in some special situations, like a scammer and a specialist, but you'll wont find that in the case of GPs, for example. Obviously you should only compare doctors on the same field (N0tch would be quite unproductive if he suddenly had to work with COBOL, for example), and between those the difference is measured in percentages, not 1000 percentages. (I can dig up the data if you want but I definitely read this when I recently had to look into diagnostic errors.)