# Should we have a tag for questions about pre-post treatment designs?

I follow (with interest) questions and answers that talk about pre-post experimental or quasi-experimental research designs. I have noted quite a few questions that ask about this particular research design (not surprising, it is a common design), although IMO our current set of tags are lacking in uniformity, and so here I want to talk about what tags should we assign to related pre-post design questions? Example questions that I am aware of are;

I'm sure others exist and would appreciate comments/answers pointing to other examples.

Current (relevant) tags in the list of questions are;

• repeated measures
• change scores
• clinical trial
• anova
• ancova
• regression
• least squares
• linear model
• intervention-analysis

I bold and because they may serve as reasonable tags already in place that could be added to all of the questions (the others are included to highlight how little the current set of tags connect the related questions). I say could because I don't necessarily think either is a great idea. The change scores tag implies a particular type of analysis (which is not always appropriate nor endorsed). Repeated measures is a terminology not frequently associated with fields I am more familiar with (sociology, criminology, economics). For instance, economists difference in difference models (e.g. Card & Krueger, 1994) are really one type of change score models. I don't think I've ever heard repeated measures used by an economist though (much related to the panel data terminology rants @Stask has mentioned in some of his answers).

In addition to this (my opinions aside) I would suggest we reference this answer by chl as a canonical response to related questions. It is not too much of a stretch to say it is still an open debate, and as such references to other literature with discussion about nuances would almost always be appropriate. As such this question in particular should be given the tag(s) we expect such questions to have in the future.

So before getting ahead of myself, should these questions all have at least one tag in common? How about a tag for pre-post-design? In additon should we cut some of the tags from these questions? Any thoughts on the subject (and how we should proceed in the future) are welcome.

• Andy, did you ever create the tag? There's another question now where it could be used: pre-post-test-with-control-group. – gung - Reinstate Monica Nov 27 '12 at 4:03
• @gung I did not (I'm pretty sure I've seen other questions since then as well that would qualify). When I get a chance I will work on a tag wiki for this and re-tag a few questions at a time on the site (since there doesn't seem to be any opposition). – Andy W Nov 27 '12 at 11:43

I am happy with your suggestion to create a pre-post-design tag which may be helpful to better identify questions dealing with specific experimental designs. (In passing I noticed we don't even have a tag for quasi-experimental designs.)
It seems to me that the repeated-measures tag does not necessarily cover exactly the same topic as it can be associated to longitudinal data, or repeated measurements in designed experiments (e.g., in psychology), to name a few. As such, pre-post design would just belong or be a sub-category of that more general tag. Also, change-scores are more alike 'derived variables', as stated in plain English, while they are also suggestive of a statistical technique for analyzing two-group parallel design, which is not necessarily the way to go.