Dear Colleagues:
I am analyzing data from a crossover study using ANOVA or ANCOVA. The dependent variable is the difference between baseline and end of treatment for some physiological measure. With UNIANOVA my syntax looks like this: UNIANOVA Outcome BY Period Sequence Product Subject /RANDOM=Subject /METHOD=SSTYPE(3) /INTERCEPT=INCLUDE /DESIGN=Sequence Period Product Subject(Sequence). This gives me exactly the same results as MIXED Outcome BY Period Sequence Product Subject /FIXED=Sequence Period Product  SSTYPE(3) /METHOD=REML /print=solution /REPEATED=Product  SUBJECT(Subject) COVTYPE(UN). However, when I add the baseline value of the outcome measure as a covariate, my syntax looks like this: UNIANOVA Outcome BY Period Sequence Product Subject with Baseline /RANDOM=Subject /METHOD=SSTYPE(3) /INTERCEPT=INCLUDE /DESIGN=Sequence Period Product Subject(Sequence) Baseline. vs. MIXED Outcome BY Period Sequence Product Subject with Baseline /FIXED=Sequence Period Product Baseline  SSTYPE(3) /METHOD=REML /print=solution /REPEATED=Product  SUBJECT(Subject) COVTYPE(UN). and the results of the two procedures are completely different. What am I doing wrong? What is the difference between my two ANCOVA models? Thank you, Andreas  Sent from: http://spssxdiscussion.1045642.n5.nabble.com/ ===================== To manage your subscription to SPSSXL, send a message to [hidden email] (not to SPSSXL), with no body text except the command. To leave the list, send the command SIGNOFF SPSSXL For a list of commands to manage subscriptions, send the command INFO REFCARD 
There is at least the difference in METHOD. MIXED uses REML or ML to
estimate variance components. UNIANOVA/GLM computes them from
expected mean squares (ANOVA method). With designes more or less
complex, that may produce difference.
12.10.2017 20:08, AndreasV пишет:
Dear Colleagues: I am analyzing data from a crossover study using ANOVA or ANCOVA. The dependent variable is the difference between baseline and end of treatment for some physiological measure. With UNIANOVA my syntax looks like this: UNIANOVA Outcome BY Period Sequence Product Subject /RANDOM=Subject /METHOD=SSTYPE(3) /INTERCEPT=INCLUDE /DESIGN=Sequence Period Product Subject(Sequence). This gives me exactly the same results as MIXED Outcome BY Period Sequence Product Subject /FIXED=Sequence Period Product  SSTYPE(3) /METHOD=REML /print=solution /REPEATED=Product  SUBJECT(Subject) COVTYPE(UN). However, when I add the baseline value of the outcome measure as a covariate, my syntax looks like this: UNIANOVA Outcome BY Period Sequence Product Subject with Baseline /RANDOM=Subject /METHOD=SSTYPE(3) /INTERCEPT=INCLUDE /DESIGN=Sequence Period Product Subject(Sequence) Baseline. vs. MIXED Outcome BY Period Sequence Product Subject with Baseline /FIXED=Sequence Period Product Baseline  SSTYPE(3) /METHOD=REML /print=solution /REPEATED=Product  SUBJECT(Subject) COVTYPE(UN). and the results of the two procedures are completely different. What am I doing wrong? What is the difference between my two ANCOVA models? Thank you, Andreas  Sent from: http://spssxdiscussion.1045642.n5.nabble.com/ ===================== To manage your subscription to SPSSXL, send a message to [hidden email] (not to SPSSXL), with no body text except the command. To leave the list, send the command SIGNOFF SPSSXL For a list of commands to manage subscriptions, send the command INFO REFCARD ===================== To manage your subscription to SPSSXL, send a message to [hidden email] (not to SPSSXL), with no body text except the command. To leave the list, send the command SIGNOFF SPSSXL For a list of commands to manage subscriptions, send the command INFO REFCARD 
Kirill Orlov wrote
> There is at least the difference in METHOD. MIXED uses REML or ML to > estimate variance components. UNIANOVA/GLM computes them from expected > mean squares (ANOVA method). With designes more or less complex, that > may produce difference. In this particular case, the results differ substantially depending on whether I use the MIXED or the UNIANOVA procedure (and only if baseline is added as a covariate). Apart from the fact that the exact method to be used should be prespecified in a confirmatory investigation, which of the two methods would be the more appropriate one for the analysis of a crossover trial?  Sent from: http://spssxdiscussion.1045642.n5.nabble.com/ ===================== To manage your subscription to SPSSXL, send a message to [hidden email] (not to SPSSXL), with no body text except the command. To leave the list, send the command SIGNOFF SPSSXL For a list of commands to manage subscriptions, send the command INFO REFCARD 
In reply to this post by AndreasV
It bothers me to see Baseline as a covariate when it was used to compute each Outcome.
Please clarify some points. Two conditions? How many Periods are there for each condition? Do data exist as, say, Baseline, A1, A2, B1, B2 for treatments A and B? (and not where Baseline is the A1 period)
DO the widely different results include matching d.f.'s? Were there any warning messages as part of the output for either?
 Rich Ulrich From: SPSSX(r) Discussion <[hidden email]> on behalf of AndreasV <[hidden email]>
Sent: Thursday, October 12, 2017 1:08:17 PM To: [hidden email] Subject: Analysis of covariance: Different results using UNIANOVA or MIXED Dear Colleagues:
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I am analyzing data from a crossover study using ANOVA or ANCOVA. The dependent variable is the difference between baseline and end of treatment for some physiological measure. With UNIANOVA my syntax looks like this: UNIANOVA Outcome BY Period Sequence Product Subject /RANDOM=Subject /METHOD=SSTYPE(3) /INTERCEPT=INCLUDE /DESIGN=Sequence Period Product Subject(Sequence). This gives me exactly the same results as MIXED Outcome BY Period Sequence Product Subject /FIXED=Sequence Period Product  SSTYPE(3) /METHOD=REML /print=solution /REPEATED=Product  SUBJECT(Subject) COVTYPE(UN). However, when I add the baseline value of the outcome measure as a covariate, my syntax looks like this: UNIANOVA Outcome BY Period Sequence Product Subject with Baseline /RANDOM=Subject /METHOD=SSTYPE(3) /INTERCEPT=INCLUDE /DESIGN=Sequence Period Product Subject(Sequence) Baseline. vs. MIXED Outcome BY Period Sequence Product Subject with Baseline /FIXED=Sequence Period Product Baseline  SSTYPE(3) /METHOD=REML /print=solution /REPEATED=Product  SUBJECT(Subject) COVTYPE(UN). and the results of the two procedures are completely different. What am I doing wrong? What is the difference between my two ANCOVA models? Thank you, Andreas  Sent from: http://spssxdiscussion.1045642.n5.nabble.com/ ===================== To manage your subscription to SPSSXL, send a message to [hidden email] (not to SPSSXL), with no body text except the command. To leave the list, send the command SIGNOFF SPSSXL For a list of commands to manage subscriptions, send the command INFO REFCARD 
The study was a simple twotreatment twoperiod crossover design with
(baseline A > drug A) followed by (baseline B > drug B) or vice versa in randomized order (i.e., two sewuences). There is a regulatory guideline that needs to be followed and which specifies the following requirements: "When the primary analysis is based on a continuous outcome there is commonly the choice of whether to use the raw outcome variable or the change from baseline as the primary endpoint. Whichever of these endpoints is chosen, the baseline value should be included as a covariate in the primary analysis. The use of change from baseline with adjustment for baseline is generally more precise than change of baseline without adjustment. Note that when the baseline is included as a covariate in a standard linear model, the estimated treatment effects are identical for both ‘change from baseline’ (on an additive scale) and the ‘raw outcome’ analysis. Consequently if the appropriate adjustment is done, then the choice of endpoint becomes solely an issue of interpretability." I first did the analysis using treatment as a factor and change from baseline as the dependent variable, and the results for UNIANOVA and MIXED were identical. Then I added the baseline value as a covariate using the syntax above. Now the d.f.s for all main effects were different between UNIANOVA and MIXED, and so were the F and pvalues. Andreas  Sent from: http://spssxdiscussion.1045642.n5.nabble.com/ ===================== To manage your subscription to SPSSXL, send a message to [hidden email] (not to SPSSXL), with no body text except the command. To leave the list, send the command SIGNOFF SPSSXL For a list of commands to manage subscriptions, send the command INFO REFCARD 
Administrator

Andreas, providing a small sample dataset (e.g., via DATA LIST) that
illustrates the problem will increase the likelihood that someone will help you work out what is going on. Cheers, Bruce AndreasV wrote > The study was a simple twotreatment twoperiod crossover design with > (baseline A > drug A) followed by (baseline B > drug B) or vice versa in > randomized order (i.e., two sewuences). There is a regulatory guideline > that > needs to be followed and which specifies the following requirements: > > "When the primary analysis is based on a continuous outcome there is > commonly the choice of whether to use the raw outcome variable or the > change > from baseline as the primary endpoint. Whichever of these endpoints is > chosen, the baseline value should be included as a covariate in the > primary > analysis. The use of change from baseline with adjustment for baseline is > generally more precise than change of baseline without adjustment. Note > that > when the baseline is included as a covariate in a standard linear model, > the > estimated treatment effects are identical for both ‘change from baseline’ > (on an additive scale) and the ‘raw outcome’ analysis. Consequently if the > appropriate adjustment is done, then the choice of endpoint becomes solely > an issue of interpretability." > > I first did the analysis using treatment as a factor and change from > baseline as the dependent variable, and the results for UNIANOVA and MIXED > were identical. Then I added the baseline value as a covariate using the > syntax above. Now the d.f.s for all main effects were different between > UNIANOVA and MIXED, and so were the F and pvalues. > > Andreas > > > >  > Sent from: http://spssxdiscussion.1045642.n5.nabble.com/ > > ===================== > To manage your subscription to SPSSXL, send a message to > LISTSERV@.UGA > (not to SPSSXL), with no body text except the > command. To leave the list, send the command > SIGNOFF SPSSXL > For a list of commands to manage subscriptions, send the command > INFO REFCARD   Bruce Weaver [hidden email] 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 email, please use the address shown above.  Sent from: http://spssxdiscussion.1045642.n5.nabble.com/ ===================== To manage your subscription to SPSSXL, send a message to [hidden email] (not to SPSSXL), with no body text except the command. To leave the list, send the command SIGNOFF SPSSXL 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 email, please use the address shown above. 
In reply to this post by AndreasV
Thanks for the detail. Here is what I gather: The difference in d.f. in the results says that the two models are different in hypotheses, for whatever reason.
I asked about "warnings" because I did not know what the choices were for periods, and whether
the ANOVA might have found a redundant column in its matrix. From the note you provide on using Baseline as covariate, I gather that you are presenting only two "times" to the analyses. The "Period"
variable in the analyses is a dichotomy: it shows the 2nd vs. 4th data point, where the two Baselines
are 1 and 3. That looks okay.
For these programs: I don't know how you test for equality of regression coefficients. Or for
nodifferences at baseline. Those are among the assumptions for Crossover.
SSType3 was never my default, but if you have equal Ns,that should make no difference.
What I can offer next is a question of whether dropping "Intercept" helps in the covariate model; and,
what options exist that describe what to do with covariates in "Repeated"?
 Rich Ulrich From: SPSSX(r) Discussion <[hidden email]> on behalf of AndreasV <[hidden email]>
Sent: Thursday, October 19, 2017 4:18:11 PM To: [hidden email] Subject: Re: Analysis of covariance: Different results using UNIANOVA or MIXED The study was a simple twotreatment twoperiod crossover design with
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(baseline A > drug A) followed by (baseline B > drug B) or vice versa in randomized order (i.e., two sewuences). There is a regulatory guideline that needs to be followed and which specifies the following requirements: "When the primary analysis is based on a continuous outcome there is commonly the choice of whether to use the raw outcome variable or the change from baseline as the primary endpoint. Whichever of these endpoints is chosen, the baseline value should be included as a covariate in the primary analysis. The use of change from baseline with adjustment for baseline is generally more precise than change of baseline without adjustment. Note that when the baseline is included as a covariate in a standard linear model, the estimated treatment effects are identical for both ‘change from baseline’ (on an additive scale) and the ‘raw outcome’ analysis. Consequently if the appropriate adjustment is done, then the choice of endpoint becomes solely an issue of interpretability." I first did the analysis using treatment as a factor and change from baseline as the dependent variable, and the results for UNIANOVA and MIXED were identical. Then I added the baseline value as a covariate using the syntax above. Now the d.f.s for all main effects were different between UNIANOVA and MIXED, and so were the F and pvalues. Andreas  Sent from: http://spssxdiscussion.1045642.n5.nabble.com/ ===================== To manage your subscription to SPSSXL, send a message to [hidden email] (not to SPSSXL), with no body text except the command. To leave the list, send the command SIGNOFF SPSSXL For a list of commands to manage subscriptions, send the command INFO REFCARD 
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