An old woman took her husband to the doctor. The doctor checked the husband's pulse, then told the woman, "I'm sorry, your husband is dead."
The woman was shocked. "I don't believe it. Are you sure? I want to be absolutely sure, are there any other tests you can do?"
The doctor responded, "I'm quite sure, but if you'd like we do have some alternative tests that we can perform."
"YES! I have to be absolutely certain."