I bought a house in 1998. This house cost $79k. At the time my salary wasn't super high, so I had to cut back on expenses. However, I wanted a cat. So I went to the SPCA to look for a cat. There, I saw this wonderful, big, fat, black cat. The sign said this cat was spayed, in good health and ready to go. So i paid the $35 and off we went. The cat was so big that it couldn't go #2 in the litter box. She would go right outside the box.
One day I threw a party at the new house. All my friends showed up, brought house warming gifts, and we drank pretty good. One of my buddy's picked up the cat, held it belly up and said, this cat has some lumps under it's belly. That didn't sound good. So the next day I brought the cat to the vet. I said this cat has some lumps under her belly, are they tumors? Then I headed to work.
Later that day, I got a call from the vet. They said, Mr. Bloom, we have some good news and some bad news. First of all, the cat does not have tumors. Secondly, the cat is a boy. Those are its genitals. Because the cat is so fat and it's fur is all black, they're difficult to see. Ay caramba. Wasn't expecting that. So I picked up the cat, whose name was AJay, luckily the name could go either way, and we went home. There I went back to look for the paperwork from the SPCA, sure enough the cat had a girls name, the female box was checked and it indicated she was spayed, not neutered.
So what the moral of the story? Sometimes the data is bad from the beginning. And assumptions are made based on that information. And sometimes the action resulting from bad data is totally incorrect. Sometimes we discover the root cause, other times not. So beware.