Date:         Tue, 27 Sep 2005 16:51:04 +0200
Reply-To:     fvillamayor-research@ferrergrupo.com
Sender:       "SPSSX(r) Discussion" <SPSSX-L@LISTSERV.UGA.EDU>
From:         Frederic Villamayor <fvillamayor-research@ferrergrupo.com>
Subject:      Help on MIXED
Content-Type: text/plain; charset="ISO-8859-1"

Dear co-listers:

I  need some help on the proper syntax to run a MIXED procedure on my 
data.

The experimental design is as follows:

We've got three volunteers. From each volunteer  a sample of skin is taken 

The samples are divided in different aliquots (replicates) and subjected 
to two possible treatments. The concentration of a certain substance (PNC) 

is repeatedly meassured along 12 different times on three replicates per 
treatment  on volunteer 1, three replicates for treatment 1 and 2 
replicates for treatment 2 on volunteer 2, and only one replicate per 
treatment on volunteer 3. It is clear enough? Maybe this table helps:

VOL     TREAT   REPL    TIME
1       1       1       1-2-3-4-5-6-7-8-9-10-11-12
                2       1-2-3-4-5-6-7-8-9-10-11-12
                3       1-2-3-4-5-6-7-8-9-10-11-12
        2       1       1-2-3-4-5-6-7-8-9-10-11-12
                2       1-2-3-4-5-6-7-8-9-10-11-12
                3       1-2-3-4-5-6-7-8-9-10-11-12
2       1       1       1-2-3-4-5-6-7-8-9-10-11-12
                2       1-2-3-4-5-6-7-8-9-10-11-12
                3       1-2-3-4-5-6-7-8-9-10-11-12
        2       1       1-2-3-4-5-6-7-8-9-10-11-12
                2       1-2-3-4-5-6-7-8-9-10-11-12
                3       1-2-3-4-5-6-7-8-9-10-11-12
3       1       1       1-2-3-4-5-6-7-8-9-10-11-12
                2       1-2-3-4-5-6-7-8-9-10-11-12
                3       1-2-3-4-5-6-7-8-9-10-11-12
        2       1       1-2-3-4-5-6-7-8-9-10-11-12
                2       1-2-3-4-5-6-7-8-9-10-11-12
                3       1-2-3-4-5-6-7-8-9-10-11-12

What I'm trying to test if that the treatment influences on the 
concentration of PNC. After repeated assays and errors, I've got this 
syntax, reflecting (I expect so...) that the experimenta subjects are the 
3 volunteers, than the replicates are a random factor nested for each 
combination of treatment and volunteer, that repeated meassures are taken 
for each combination ot time, replicate and treatment, and thatthe fixed 
effects on the model are treatment, time and its interaction. Furthermore, 

I comparetreatments on each timepointadjusting for multipla comparisons.

MIXED pnc BY vol treat repl time
  /FIXED = treat time time*treat
  /RANDOM repl(treat*vol)) | SUBJECT(vol) COVTYPE(AR1)
  /REPEATED = time*repl*treat | SUBJECT(vol) COVTYPE(AR1)
  /EMMEANS = TABLES(time*treat) COMPARE(treat) ADJUST(BONFER) .

The results are convenient to me, but It would be splendid if I can read 
some comments from any of you, since I'm rather novice with this command 
and I'm not sure if I'm doing what I really want to do.

Thanks in advance.


Frederic

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Frederic Villamayor
Unitat de Bioestadística
Àrea de Desenvolupament Preclínic
CIDF Ferrer Grupo
Juan de Sada, 32
08028 ? Barcelona
Espanya

E-mail: fvillamayor-research@ferrergrupo.com
Tel: +34 935093236
Fax: +34 934112764
WWW: www.ferrergrupo.com

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"Sanity is not statistical"
1984 (George Orwell)