One day Bill complained to his friend, "My elbow really hurts, I guess I should see a doctor." His friend offered, "Don't do that. There's a computer at the drug store that can diagnose anything quicker and much cheaper than a doctor. Simply put in a sample of your urine and the computer will diagnose your problem and tell you what you can do about it. It only costs $10." 

Bill figured he had nothing to lose, so he filled a jar with a urine sample and went to the drug store. Finding the computer, he poured in the sample and deposited the $10. The computer started making some noise and various lights started flashing. After a brief pause out popped a small slip of paper on which was printed: You have tennis elbow. Soak your arm in warm water. Avoid heavy lifting. It will be better in two weeks. 

Late that evening while thinking how amazing this new technology was and how it would change medical science forever, he began to wonder if this machine could be fooled. He decided to give it a try. He mixed together some tap water, a stool sample from his dog and urine samples from his wife and daughter. To top it off, he masturbated into the concoction. 

He went back to the drug store, located the machine, poured in the sample and deposited the $10. The computer again made the usual noise and printed out the following message: Your tap water is too hard. Get a water softener. Your dog has worms. Get him vitamins. Your daughter is using cocaine. Put her in a rehabilitation clinic. Your wife is pregnant with twin girls. They aren't yours. Get a lawyer. And if you don't stop jerking off, your tennis elbow will never get better.