Because doing controlled trials is how you come about that knowledge. Otherwise ...

c3534l on Feb 16, 2018 | parent | context | favorite | on: Many medical devices on the market have undergone ...

Because doing controlled trials is how you come about that knowledge. Otherwise you're just guessing. You can guess something is safe, but until you try it for real in a systematic way, that's all it is, a guess. That's not knowledge.