A man goes into a bar. He finds himself drinking next to two men in dusty working clothes.

"Can I ask what you two do for a living?" he says.
"Sure. We're both bricklayers. And how about you?"
"Oh, I'm an electronic engineer."
"What's that?"
"Oh, I design computers and peripherals. In fact, I've just been awarded a patent for a device I've just invented. It allows microchip components to be located to within 0.0000314 of a nanometer, with 99.9997 percent reliability".

"Ah, you'd be no good in our job, then", says one of the brickies. "Our gaffer says we have to be spot on, every time."