Ignorance of basic statistical methods

There's no point in locking your car doors. If someone wants in, they'll just break the glass, and then you'll have the cost of broken glass on top of the theft to deal with.

Most of the people who die of heart failures in hospitals have had defibrillators applied to them just before they died. Better make sure not to let them use a defibrillator on you.

In the history of mankind, more than 80% of people who have eaten tomatoes subsequently died. Tomatoes are poison!

Correctly identifying the sample is key in saying anything meaningful about it.