A ph question for the mathmatically inclined

[Madmax478]

WARNING! NO MATH BELOW...

PERSONALLY, the pH test kits from API are absolutely horrible in my experience. I have found using more than 1 testing method will often yield better results or at least tell you if one of the test kits or devices you have is wrong.

I have gone through 3 API pH test kits. For some reason, they never give a good reading. The regular pH test vs. the high pH test always give different results from the same kit!!! Not to mention both tests give readings that don't concur with 2 other methods, another chemical test kit and a digital pH meter.

So what method of testing PH do you find that is the most accurate?