Texas sharpshooter fallacy
The Texas sharpshooter fallacy is an informal fallacy that erroneously stresses patterns in data while ignoring differences. The analogy is that a Texan is firing a number of shots at the side of a barn. He paints a target at the centre of the largest cluster of bullet holes and claims he is a good shot.
The fallacy occurs when forming a hypothesis based on data and then claiming the original data supports the hypothesis. This is not statistically valid because true patterns and coincidences cannot be distinguished. The proper procedure is to verify the hypothesis on new data. In other words, the hypothesis must be stated before comparing it to the data.
The fallacy also occurs when claiming a random occurrence is significant without any justification. If in a game of poker you are fairly dealt a random set of cards, that set of cards is just as likely as any other.
The likely cause of the fallacy is a cognitive bias in humans called apophenia, which is the tendency to perceive false patterns in random data.