Yeah, there's always a standard error but for the sake of accuracy you might want to try to find the value of that standard error using averages from other test kits...i understand that calcium isn't important to you though if you don't keep hard corals (even LPS have a sort of skeleton though)...just an fyi, not only might you want to find a range for the standard error but recalibrate fairly frequently. I work with professional spectrophotometers at a university and even they need to be recalibrated fairly frequently. I do understand that you don't like testing. I do feel like theres less room for error when dealing with titration based test kits, however, than purely colorimetric or even spectrophotometric testers depending due to the complexity involved. Chemicals are chemicals at at certain concentration and chemistry dictates they will react the same every time if performed correctly while spectrophotometers are very complex and leave plenty more room for not just user errors but internal errors as well. Again, i do fully understand the disdain towards manual testing, i personally would just prefer to invest that amount of money in other ways for my tanks.