Deciding on whether to explicitly indulge on a "Welcome to the site" message for new posters is irrelevant if there is no agreement on what defines being welcoming.
The participants on our site are outstanding people, ready to help, educate, and lead by example in the pursuit of knowledge.
However, confusion becomes all too apparent when receiving a new post at odds with the guidelines of the site. For instance, on this post Wang Nick asked a question that is probably the only real challenge in getting the main idea behind PCA - the idea that the components are contributed to by all variables. His first question. He or she starts off apologetically, "I am new in PCA..." and explains the problem. Nothing unusual; yes, asked a million times before, and answered beautifully on the site. Possibly someone in the applied sciences being thrown to the lions by a mentor, and being asked to just figure it out. Who knows?
The first comment: "How about reading some book on statistics?" with one upvote.
The point that I want to make is that CV is not a professional organization, where members are vetted through a qualifying process. Nowhere does it say that anybody without thorough comprehension of linear algebra should stay out - and how boring would it be if it did...
The truth is that we all use data all the time if we participate in the political discourse, organize our finances, work in a corporation, or even simply watch TV. People with some spark of interest look things up, and try to understand. In the process they (we) discover CV, and muster the courage to risk making a fool of ourselves posting a question. Some of the best questions are provided by wide-eyed first impressions of probability or statistical concepts on complete neophytes. I would never ask now "Who are the bayesians?". Even though I don't know much more than I knew when I did, I have read too much about it and by Andrew Gelman since I wrote the question not to feel like a complete schmuck if I were to ask it now. But I can't think of any good questions that elicit a fraction of the interest that question raised.
We don't know initially where the person comes from, what his level of mathematics is (although this is quite apparent to the more advanced users), whether they had any training in statistics before (same caveat here), or even their age. But they are showing interest. Perhaps the person asking that question will not just read, but write the next canonical book on statistics. Perhaps... a positive response to that first question...
I would propose avoiding the following for first time questions:
- Down-voting first time posts.
- Voting to close the question without a kind explanation.
- Comments ad hominem - nothing along the lines of "as you should know", "if you had done a minimum of research you wouldn't be asking this", "your question is impossible to understand, makes no sense, without providing all this information that you obviously don't know, but should", etc. Simply state the facts in a plain, simple manner.
- Assuming familiarity with tags. If it seems as though it's a homework question, ask directly and instruct how to tag it appropriately; or if interested enough to comment in the first place, why not ask a more open-ended question about the background of the post?
How much nicer and productive, and encouraging is the comment by Richard Hardy: "I cannot follow you question well [my emphasis], but it seems that you might be confused about how PCA works. The principal components are linear combinations of original variables. Asking "which variable should I retain" does not make that much sense in the context of PCA [notice he doesn't say - it makes no sense. Period... It is in the context of PCA that is lacking in meaning]." He gives the answer to the person, so that he can go back to scrutinizing whatever sources of information are at his level, but without judging. A class act.
I often think of the quote in whuber's profile: "Why waste time learning, when ignorance is instantaneous?".
So let's truly embrace in the first comments and responses the people who choose to learn, with or without "welcome to the site".