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 an 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.