I often find erroneous responses on Stack Exchange. Is there a way to flag these as wrong or false?
Also, I am not really sure how reputation works... You have to have reputation before you can do anything? Seems like a pretty big barrier to making sure answers provided are correct...
There are limited options for dealing with wrong answers on Stack Exchange, especially if you have not earned any reputation points.
You have to have reputation before you can do anything?
It definitely can seem that way, but reputation is actually required more for the minor site functions than the major ones. New users can make question or answer posts right away. As TRiG says, if you can post an answer of your own, that would give you a place to discuss the errors in the earlier answer.
Unfortunately, as Kris pointed out in a comment, knowing that an answer contains errors doesn't always imply knowing the correct answer to a question. Using an answer post just to correct another answer is not allowed, so if you can't answer the question, this is not a possible course of action.
The other ways of dealing with bad answers—flagging, comments, and downvoting—all require you to earn some reputation, and the first two are subject to fairly heavy moderation.
The current flag system allows answers to be flagged for four reasons: "spam", "rude or abusive", "not an answer", or "in need of moderator intervention". None of these is really applicable to a question that is merely incorrect. The "not an answer" flag is sometimes raised on egregiously wrong answers, but the general consensus on Meta Stack Exchange is that this flag should only be used for posts that do not even attempt to answer the question, not for posts that try and fail to answer the question correctly.
(Edit: as Tonepoet's answer mentions, there is also a fifth flag option, "very low quality", that is only available for certain recent answers. Its meaning is a bit unclear, but it also shouldn't be applied to posts that try and fail to answer the question correctly.)
Thus, flagging is rarely the right way to respond to erroneous answers.
Constructive criticism is one of the intended uses of the "Comment Everywhere" privilege, so in principle, you should be able to use comments to point out errors to the author of an answer. However, diamond moderators have the ability to delete comments, and they often will in circumstances where they feel that a comment chain has become a discussion, or if they think that it's unlikely that the post author will respond productively to the comment. A commonly expressed sentiment on Stack Exchange is that comments should be thought of as "ephemeral" and "unimportant": although I don't really agree with applying this model to comments that point out errors, it's still likely that moderators will take this perspective when dealing with your comments. Maintaining a polite tone will reduce the chance of your comments being deleted.
Comments by themselves don't have any effect on the answer, but a comment may serve as a visible note to readers that lets them know about the errors (this is especially true if the comment gets upvoted).
Downvoting is the least restricted, and most encouraged way of dealing with incorrect answers. But it also has the highest reputation limit, and each downvote on an answer costs a point of reputation. Voting affects the relative ranking of the answers to a question, and answers with a sufficiently low total score get "grayed out".
The meaning of downvotes is somewhat subjective: the tooltip for downvoting answers merely says "This answer is not useful", while the Help Center says "Voting down, also known as "casting downvotes", is how the community indicates which questions and answers are least useful. [...] Use your downvotes whenever you encounter an egregiously sloppy, no-effort-expended post, or an answer that is clearly and perhaps dangerously incorrect."
Downvotes are subject to moderation only in the sense that voting abuse (like "serial downvoting" a particular user's posts, sock-puppetry and the like) is investigated and perpetrators may be disciplined. Aside from these obvious exceptions, it's up to each user to decide whether an answer ought to be downvoted.
A downvote may optionally be accompanied by an explanatory comment. This is never required (although the site reminds users of this option in some circumstances), and opinions about when to do this vary greatly between Stack Exchange users.
You have to have reputation before you can do anything?
Without reputation, you can write questions and answers. This is also how you earn reputation, which will soon allow you to do other things, such as vote, comment, participate in chat, and edit.
It is possible to flag answers, but as has been said in comments, this is more for process violations than for incorrectness (I like that phrasing, and shall adopt it henceforth; thanks, Lawrence). If you see a wrong answer, the best thing to do for now is to ignore it and simply write your own, if you can. If yours is better supported, the voting patterns will probably place it above the wrong one anyway. If you can’t write your own answer, simply ignore it for now and come back when you have enough rep to downvote and comment. It doesn’t take long to earn rep if you provide good answers. And there will be plenty of questions you can answer.
Asking interesting questions is also a good way to gain reputation.
No, there is not. You shall have to wait until you earn the reputation to vote.
There is a flagging system, and a Very Low Quality flag that seems like it should allow you to flag some answers as false, but it is really meant for posts that are completely incomprehensible. It is not for wrong answers. If I recall correctly, some restrictions have even been placed on when a Very Low Quality flag can be raised, because of how easy it is to misunderstand.
Part of the reason there is no flag for a wrong answer is that flagging is primarily meant to alert moderators that a post should be outright deleted due to some major defect, but an answer simply being wrong does not merit deletion. The Stack Exchange system is meant to have some wrong and otherwise bad answers so that community consensus can sort their place appropriately through the voting system, because knowing which answers are poorly received can also be instructive, and not just for the people who want to know the answer to the question, but also for people who want to know how to write better answers.
Reputation limits on voting are there to help ensure that voters are trustworthy. It ensures that voters have at least some rudimentary knowledge regarding the subject, enough of an investment in the website to be expected to vote in good faith before they have the ability to do so and are not suspended for exhibiting immediately poor behavior (since a person's reputation is reduced to one point for the duration of suspension). Otherwise, you might have some random passerby voting against a whole bunch of answers just for laughs, or just out of spite. People can still do that even with the limits unfortunately, but fewer people will do it than they would otherwise, and at least it is restricted to people who have made an otherwise positive contribution to the website.
The reputation threshold for voting is relatively low though and if you start contributing to the website to prove yourself, I would suppose you could earn the privilege relatively quickly. Being awarded one bounty, five votes for your answers or fifty edits would be enough to let you cast your first vote against an erroneous answer. It would only allow you one such vote since voting against answers actually detracts from reputation, but it is only by a single point, so if you continue making positive contributions, this will eventually be rendered into a relatively insignificant amount.
The primary question here is about the quality of the content of answers here.
To answer the central question, how you notify others on SE whether an answer is correct, the oversimplified answer is that you vote.
There are many mechanisms built in to the SE software to indicate some kind of quality. There's spam or vulgar which can be flagged; there's off-topic or not the right place which can be close-voted, and there's helpfulness or correctness which can be voted.
If you think an answer is wrong you should downvote it (likewise if you think it is correct you should up-vote). And if you think just a downvote is not enough (it is swamped by upvotes by people you think are wrong), you may add a comment. Or better, you may want to give what you think is the correct answer, so that your presumably correct answer gets upvoted more.
This is the primary working of SE voting.
However, to address reputation, there are small qualifications. In the design of SE, the designers wanted to not only assess the answers, but also people. For that, there is the concept of reputation, which one gets from having questions and answers voted on (the first thing mentioned). Once you get enough reputation (answer enough questions that get upvoted), then you pass some thresholds which enable certain extra features, like the ability to comment, the ability to downvote, and so on. If you don't have enough reputation, you probably don't have enough experience with the site, and so aren't expected to be able to use those tools as expected. The idea is that people with enough rep are invested already in the quality of the site and will use those features in a quality manner.
Once you have enough rep, you'll be able to do more things, like downvote or comment to say something like "This is entirely wrong" (but of course you will want to be responsible and give reasonable justification, not leaving it at such a bald statement.
The 'barrier' or thresholds to getting features are laid out in the FAQs somewhere. At the beginning those features may seem daunting, but all it takes is a small handful of activity (getting used to the system too), and then you'll have enough rep to do all sorts of things.
