Understanding "Accurate," "Precise," And "Reliable"
Picture this: You and I are having a casual game of darts. To decide who will shoot first, we diddle for the middle—aim for the bull’s eye. Whoever lands closest to the center bull will start. As I am a chucker (totally inept), my dart nearly embeds itself in the wall. You, however, never throw woodies. Your dart not only hits the bull’s eye, it lands in the inner ring!
I reflect on past matches and see a pattern. My shots consistently hit the same spot, but unfortunately not my target. You always have your game head on and find the winning shot every time. The chemist in me recognizes that while I am precise, you are accurate plus precise. It does not cheer me up to think we are both reliable, meaning that when we play again we can be counted on to perform exactly the same way!
This analogy holds for test kits. The best ones closely approximate the actual value of the parameter in question; they are accurate. The best kits also can be counted on to give the same reading whenever the test is conducted under the same conditions; they are precise. A reliable manufacturer’s chemistries will yield accurate and precise results not only from test to test but from kit to kit, as well. At Taylor, we pride ourselves on the accuracy, precision, and reliability of our water quality tests.