Yes - the vital importance of not just knowing what the reading is on a piece of test equipment, but how to interpret that reading in order to take appropriate action. Your post, Euphfiend, reminded me of the old engineers joke (and serious warning!): Once upon a time there was a railway wheel tapper called Charlie Bloggs. He worked in a huge shunting yard, and he tapped all the wheels on all the wagons which came into the yard, checking to see if the tyres were loose on the wheel centres. If the tyre was tight, he expected to hear a nice "Dinggggg!!" , whereas if the tyre was loose, he would hear "Dunk!" And Charlie scrapped four hundred and fifty seven thousand, six hundred and nineteen wheels - and then the awful truth dawned on him. All those tyres were not loose - it was his hammer that was cracked . . .