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| From | Philip Ender <ender97@gmail.com> |
| To | statalist@hsphsun2.harvard.edu |
| Subject | Re: st: repeated factor ANOVA |
| Date | Tue, 2 Oct 2012 07:57:52 -0700 |
On 10/2/2012 James prince <jsprince26@gmail.com> wrote: Hello, I am unsure how to set-up the following problem using the ANOVA command. Any help would be appreciated. I have data on 600 liver patients, 300 assigned to one of two treatment groups (TREAT). Each had 4 biopsy (one in each quadrant: UR, UL, LR, LL) and the concentration on an enzyme (Y) measured. I also have data for sex. I know that I can used XTMIXED to do this, but I need to use ANOVA Thank you in advance, Jim -------------------------------------------------------------------------------------- This is what I did: I first tried using a repeated ANOVA but got an error: . anova y treat liver sex subj, repeat(subj) could not determine between-subject error term; use bse() option Then, If I set it up as nested, I get a result, but I am not sure if it is correct. anova y treat liver sex/ subj|liver/ ... You say you need to use -anova- but you don't say why you need to use -anova-. For balanced designs -xtmixed- and -anova- yield equivalent results although somewhat differnt p-values due to chi-square vs F-ratio. If the design is unbalance within subject then -xtmixed- is much better. With your large sample size the p-value issue should be moot. All that aside, here is the -anova- code to run your analysis without sex. The error term for treat is subj|treat. There should be a treat by liver interaction and the repeated factor is liver. anova y treat / subj|treat liver treat#liver /, repeat(liver) If you want to include sex you need to treat it as a between subject factor. The error term for the between subject factors is subj|treat#sex. You also get more interactions anova y treat sex treat#sex / subj|treat#sex liver sex#liver treat#liver sex#treat#liver /, repeat(liver) -xtmixed- code is much simpler: xtmixed y treat##sex##liver || subj:, reml var -- Phil Ender UCLA Statistical Consulting Group * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/faqs/resources/statalist-faq/ * http://www.ats.ucla.edu/stat/stata/