One day, in line at the company cafeteria, Joe says to Mike behind him, “My elbow hurts like hell. I guess I better see a doctor.”

Mike replies, “Listen, you don't have to spend all that kind of money. There's a diagnostic computer down at Wal-Mart. Just give it a urine sample and the computer will tell you what's wrong and what to do about it. It takes ten seconds and costs ten dollars—a lot cheaper than a doctor.”

So Joe deposits a urine sample in a small jar and takes it to Wal-Mart. He deposits ten dollars and the computer lights up and asks for the urine sample. He pours the sample into the slot and waits. Ten seconds later, the computer ejects a printout:

“You have tennis elbow. Soak your arm in warm water and Epson Salt. (Aisle 8) And avoid heavy activity. It will improve in two weeks. Thank you for shopping @ Wal-Mart.”

That evening, while thinking how amazing this new technology was, Joe begins wondering if the computer can be fooled. He mixes some tap water, a stool sample from his dog, urine samples from his wife and daughter, and a sperm sample for good measure.

Joe hurries back to Wal-Mart, eager to check the results. He deposits ten dollars, pours in his concoction, and awaits the results. The computer prints the following:

1. Your tap water is too hard. Get a water softener. (Aisle 9)
2. Your dog has ringworm. Bathe him with anti-fungal shampoo. (Aisle 7)
3. Your daughter has a cocaine habit. Get her into rehab.
4. Your wife is pregnant. Twins. They aren't yours. Get a lawyer.
5. Finally, if you don't stop playing with yourself, your elbow will never get better. Thank you for shopping at Wal-Mart."