After reading your response, I'm not sure if you're trying to make my case, or refute it.
Why can't you compare GoPro and Samsung? "Comparing" doesn't mean that they are identical...it just points out similarities and differences.
My point was very simple...maybe you missed it: test results being within 20% of the correct value are "good enough" for a diabetics blood glucose testing. Sure, you could go to a lab and get the exact number, but it's not necessary (too costly, takes too long, equipment too expensive, etc). I really just need to know if my blood sugar is high or low, and an idea of the magnitude so that I can make correction. "Exactly accurate" would be great, but it's not necessary for what I'm trying to accomplish.
"Within 20%" is perfectly acceptable for a handheld tester that keeps people alive. Probably good enough for people testing weed, too. It'll get more accurate as the technology advances, but for now that's what we have. And it's perfectly adequate.
You pointed out a lot of other stuff that isn't really a comparison...just a listing of how someone that's doing the test can do it incorrectly. I can assure you that a glucose reading can be botched, as well. Don't feel like dwelling on the periphery.
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