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From | David Hoaglin <dchoaglin@gmail.com> |
To | statalist@hsphsun2.harvard.edu |
Subject | Re: st: test of repeated measurements - ordinal data (likert scale) |
Date | Fri, 6 Jul 2012 07:33:17 -0400 |
Hi, Mette. The patients' responses to that question produce an ordered categorical outcome. You should be able to use -ologit- to take into account the clustered nature of the data (i.e., repeated measurements). I suggest that you not focus too early on tests. Start by making various plots of the data, to discover what form the trends take. Rabe-Hesketh and Skrondal (2012, Chapter 11) develop an example that shows the process, including the use of -ologit- with clustered data. (It's also in Chapter 7 of their second edition.) David Hoaglin Rabe-Hesketh, S. and A. Skrondal (2012). Multilevel and Longitudinal Modeling Using Stata, third edition. College Station, TX: Stata Press. On Fri, Jul 6, 2012 at 4:14 AM, Mette Olsen <meo@life.ku.dk> wrote: > Hi, > > I wish to find a test that can compare patients' evaluation of a nutritional supplement over time. > Patients are asked the same questions (e.g.. "how did you overall find the supplement?" - 'dislike very much' 'dislike' ' indifferent' 'like' or 'like very much') after 2 weeks, 1, 2 and 3 months of supplementation, respectively. > I wish to know if there is a trend towards improved/worsened evaluation during the supplementation period, but I am not sure which type of test I should use. I have been suggested using xtmixed models but am not sure if the test allows for non-parametric data? I've also been suggested ologit but I'm not sure it can be used for repeated measurements in the same group. > > I look forward to learning more! Thanks in advance. > Mette Frahm Olsen, > PhD stud * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/