```Date: Thu, 2 Feb 2012 17:39:22 -0800 Reply-To: Bruce Weaver Sender: "SPSSX(r) Discussion" From: Bruce Weaver Subject: Re: 2x2 Latin square design analysis help In-Reply-To: Content-Type: text/plain; charset=us-ascii But as David noted, the 4 conditions are formed by the 2x2 combination of two binary variables. With the usual coding (i.e., 1 = Yes, 0 = No): D E Description --------------------- 0 0 Control 1 0 Diet, No Exercise 0 1 Exercise, No Diet 1 1 Diet and Exercise If the outcome variable was measured at both baseline and followup, then the preferred approach, arguably, would be a 2x2 ANCOVA, which is equivalent to an ordinary least squares regression model as follows: Y1 = b0 + b1*Y0 + b2*D + b3*E + b4*D*E + error where Y1 = outcome variable at followup Y0 = outcome variable at baseline D and E are as shown above, and D*E = their product. Of course one /could/ run this model using MIXED, but for users not familiar with MIXED (and I get the impression the OP is not), it will be much easier to run it via UNIANOVA (Analyze - GLM - Univariate, with D and E entered as "fixed factors", and Y0 as a "covariate", and the D*E interaction included). Another important question David raised (and I don't recall seeing an answer) is whether there was random assignment to the 4 cells. There's my two cents! R B wrote > > From what I can tell, you have one between-subjects variable (Condition) > which has four levels (Diet, Exercise, Diet+Exercise, Control) and one > within-subjects variable (Time) which has two levels (baseline, > post-intervention). This is commonly referred to as a mixed ANOVA (not to > be confused with the MIXED procedure). You could analyze your data by > fitting a general linear model or linear mixed model in SPSS. I don't have > time to write code for you at the moment, but quite frankly, there must be > numerous SPSS examples online. Bottom line is that you need to take into > account correlation among residuals obtained by repeated observations of > each subject. You can write specific contrasts of interest using the > appropriate subcommand. I am always in favor of using the subcommand which > requires that you understand the coefficient (L) matrix. > > Ryan > > On Thu, Feb 2, 2012 at 12:08 PM, Sur1605 <surabhi1605@> wrote: > >> Thanks David for such an amazing description. This is exactly how i tried >> doing it before i posted my question on this forum. But everytime i >> analysed >> my data somehow it gave me this message: >> "Post hoc tests are not performed for Diet because there are fewer than >> three groups. >> Post hoc tests are not performed for Ex because there are fewer than >> three >> groups." >> >> Basically its not able to perform the posthoc analysis. I thought i was >> doing something wrong in feeding in the data in the spreadsheet. >> >> And yes, i measured the same variables before and after the trial. Looks >> like i will have to reconsider the choice of test being used here. >> >> Thanks a lot for your help. >> >> Sb >> >> >> >> -- >> View this message in context: >> http://spssx-discussion.1045642.n5.nabble.com/2x2-Latin-square-design-analysis-help-tp5446710p5451327.html >> Sent from the SPSSX Discussion mailing list archive at Nabble.com. >> >> ===================== >> To manage your subscription to SPSSX-L, send a message to >> LISTSERV@.UGA (not to SPSSX-L), with no body text except the >> command. To leave the list, send the command >> SIGNOFF SPSSX-L >> For a list of commands to manage subscriptions, send the command >> INFO REFCARD >> > ----- -- Bruce Weaver bweaver@lakeheadu.ca http://sites.google.com/a/lakeheadu.ca/bweaver/ "When all else fails, RTFM." NOTE: My Hotmail account is not monitored regularly. To send me an e-mail, please use the address shown above. -- View this message in context: http://spssx-discussion.1045642.n5.nabble.com/2x2-Latin-square-design-analysis-help-tp5446710p5452480.html Sent from the SPSSX Discussion mailing list archive at Nabble.com. ===================== To manage your subscription to SPSSX-L, send a message to LISTSERV@LISTSERV.UGA.EDU (not to SPSSX-L), with no body text except the command. To leave the list, send the command SIGNOFF SPSSX-L For a list of commands to manage subscriptions, send the command INFO REFCARD ```

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