Perhaps the most difficult aspect of evaluating inductive arguments is determining the strength of the argument. This is because inductive arguments can only give us probable (i.e., more likely than not) conclusions. And, probability is a continuum; to say a conclusion is more likely than not means it falls somewhere between 51% and 99.999...% probability. The goal of induction is to get as close to 100% as possible, knowing full well we will never, ever reach 100% certainty.
This is what makes inductive reasoning so very different from deductive reasoning. In deduction, a properly formed argument is valid: the conclusion follows necessarily from the premises. Any valid argument will be just as valid as any other valid argument. There are no degrees of validity.
But, in inductive reasoning we have to deal with the fact that the conclusion of any argument could be stronger or weaker, depending on the amount, relevance, and clarity of the evidence provided. Failing one of these three criteria causes an informal fallacy. In that case we would judge the argument to be weak.