Argumentum ad Ignorantiam:

ar·gu·men·tum ad ig·no·ran·ti·am

 *It asserts that a proposition is neither true or false because of lack or absence of evidence or proof to the contrary

*Latin meaning argument from ignorance

In other words, Argument from ignorance is something that is true or false, with having little to no evidence

Someone would use this fallacy as a way to have others doubt themselves or their belief. It is used in science and in the court of law.

A person would use this fallacy when they have no evidence, but want to be right.

Tonight was different than any other night in Quarter. It was the food festival. People from all over the world came. Well, the ones who did come said they traveled the world so, everyone is like them and they also came from all over. Everyone looks so happy and is smiling which means they're excited for tonight!