Hi Mite Tiror! The label "fallacy of sufficiency" is a general reference to a host of different problems that can exist in inductive reasoning. Think of it this way, since inductive arguments can only ever give us degrees of probability regarding their conclusions, we want to get as much evidence as possible that our conclusion is true. But there are a myriad of ways we might fail to achieve sufficient evidence to make our conclusion more probable than not. So, appealing to inappropriate authority, or claiming that a conclusion follows because it hadn't been disproven (i.e., appeal to ignorance), or jumping to a generalization based on too few observations (i.e., hasty generalization), or weak analogies, or false causes, etc. would all be different versions of fallacies of sufficiency. In each different type, we have failed to provide a sufficient amount of evidence to make our conclusion more likely than not. Hope that helps!
