Hey - dont be lured into a false sence of security tho people. They may be precise, but we have no idea if they are accurate!
You need to be able to compare against true values in order to determine accuracy. i.e. take a pH5 solution and if the tesk kit says pH5 - then spot on. Accurate and precise. If the test kit says pH5.5 then its still precise - but not accurate.
I use tetra liquid test kits, no idea how accurate they are.
Would like to test the tests aginst a set of "standard solutions" of known value to see whether they do actually work, or if they simply work well enough for us fishkeepers.