# Should we de-synonymize dummy-variable-trap and categorical-encoding?

Sorry for bringing this up again.

I created a tag yesterday. As I wrote, I was doubtful that synonymizing it to is helpful. By now I am not doubtful any more: I believe it is not helpful. Unfortunately, the synonym has already been established.

Take a look at questions about the dummy variable trap. I have already retagged some of them . Mouse over the tag at one of those questions. Picture a user who is hazy enough about the trap to ask a question here. Will the tag wiki excerpt for (which now is the same as for the synonym ) be helpful for them? Here it is:

Representing categorical variables as sets of numerical variables. Necessary in many types of analysis for them to process categorical data. A common example is using a categorical predictor in regression/ANOVA via dummy coding, effect coding, Helmert coding, user-defined contrasts, etc.

I don't think this will help the user in any way. In particular, the links to questions that actually explained what the trap is, why it occurs, what the consequences are, and how to avoid it, which I included in the tag wiki are of course now gone that it has been synonymized.

Yes, the occurs only in . The latter is a necessary condition for the former. Does that mean that the two are synonyms? No. Does that mean that questions with the latter tag are usually helpful for someone asking about the former? I don't think so.

I propose de-synonymizing the two tags again. I can reconstruct the tag wiki and excerpt for .

• It can be done. It is fine for me, I don't have any feelings for or against it. – Tim Jul 18 at 8:52
• I agree, especially your argument about the person asking is convincing: It may be hard to see how questions related by the tag categorical-encoding are useful for someone asking about the dummy variable trap. Simply looking through the questions currently tagged as categorical-encoding will show that this is the case. – Frans Rodenburg Jul 18 at 12:46

Maybe, but I'm not sure. Note that my answer / suggestion to make it a synonym was well upvoted (+8) with no downvotes or dissenting comments for nearly two weeks before I went ahead with making the synonym. You posted a dissenting comment yesterday, which now has 1 upvote, but it's not clear if it was before or after I made the synonym. I do think it was reasonable to interpret the situation as a consensus for making the synonym at the time. Of course, that doesn't guarantee a synonym is the best choice and we can always delete the mapping with little difficulty.

If I imagine a user who wants to ask a question here about the dummy variable trap, and who has (at best) a hazy grasp of the idea, I don't picture them trying to learn about it by mousing over the tag. Instead, I imagine them trying to ask a question. I figure they would have some title with "dummy variable trap" in it, and would also type that in the tags field. If someone were to do that under the status quo, they would see something like the following:

That is, the similar questions section would show links to some relevant, existing threads, and the tag suggestions would include [dummy-variable-trap], with it's appropriate excerpt. (After they select [dvt] and post the question, [dvt] would be silently replaced by [ce], but many people don't even notice that.)

Alternatively, I might imagine such a user searching on the terms "dummy variable trap". If I search on CV, I get this. That is, the synonym didn't impair the search. Searching Google is fine as well.

I think the issue is how the synonym affects searching on the tag (which I suspect primarily users more familiar with SE would do), and how having the mapping vs. not affects how well the information on the site is organized.

I'm open to arguments on that issue. In truth, I wasn't married to the idea of making the synonym beforehand. But I continue to lean towards having the synonym—call it 60-40 for.

• Your argument seems to hinge on the tag wiki excerpt for [dvt] still visible when trying to tag a new question with it. Right? However, this only happens because the synonym has not been yet merged. Once it's merged (SE encourages us to merge all well-established tag synonyms, and this has been our policy as well), nobody will ever see its wiki excerpt anymore. I think we had such a situation previously and you argued for never fully merging that synonym and leaving 1 Q with the synonymized tag (in this case [dvt]) intact but I still don't think it's a good approach. – amoeba Jul 19 at 9:06