A recent question was closed because it already has an answer at another question. I cast the final vote because I believe that the following test is a reliable guide for casting "duplicate" close votes:
Consider two questions, A and B. Question A precedes question B in time. Questions A and B need not be related in what they ask. If any answer to Question A contains a statement which reasonably answers Question B (whether or not it is a good answer to either of A or B), then there is a rebuttable presumption that Question B is a duplicate of Question A. The presumption is rebutted only if Question A fails to generate five close votes. The people who vote to close need not be knowledgeable as to whether the answer to question A is actually also a good answer to question B.
Did I act within community guidelines by casting a close vote?
A proposed duplicate to this post (both the question and its answer) treats as equivalent two types of "duplicates": (i) pairs of questions which are similar, and (ii) pairs of questions which have attracted similar answers. This post calls for a more nuanced approach to duplicates, and I wouldn't click the check mark for the answer that the proposed duplicate got.