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From |
David Airey <[email protected]> |

To |
[email protected] |

Subject |
Re: st: RE: RE: Covariates in ANOVAs |

Date |
Fri, 15 May 2009 08:38:16 -0500 |

-Dave On May 14, 2009, at 11:30 PM, Miss Gina Micke wrote:

Thanks for your input. Maybe I didn't make myself clear enough re"age range". Age range refers to actual age in days at eachmeasurement. As all subjects were measured on the same day at eachmeasurement event, the difference between subject ages is the sameat each measurement event, so age at first measurement would be thedata in the "age range" variable. Do you still think this should beinlcuded as a categorical variable?________________________________________From: [email protected] [[email protected]] on behalf of Joseph Coveney [[email protected]]Sent: Friday, 15 May 2009 11:48 AM To: [email protected] Subject: st: RE: Covariates in ANOVAs Miss Gina Micke wrote:I would like to know how to control for an independent continuousvariable whenusing a repeated measures ANOVA. I have a 2x2 factorial designexperiment withmales and females in each of the treatment groups (T1 & T2) measuredat multiple"events", each subject assigned an "id". The subjects are alldifferent ages soI would like to be able to control for the effect of "age range".If I didn't have "age range" as a covariate my model would be asfollows:anova x T1 T2 sex T1*T2 T1*sex T2*sex T1*T2*sex/id|T1*event T2*eventT1*T2*eventsex*event sex*T1*event sex*T2*event T1*T2*sex*event, repeated(event)partialbse(id|T1*T2*sex)Do I use the ANCOVA and cont(age range) command? Is this output theeffects ofmy fixed factors taking into account the effect of age range? --------------------------------------------------------------------------------First, the command line text shown doesn't look at all like correctsyntax.Second, by the name of it, a variable called "age range" would becategoricaland so you would not be using the -continuous()- option for it in -anova-.Unless you have balanced data (equal representation of age rangeswithin eachfactorial cell, as well as equal sex-by-treatment group cell sizesmaintainedthroughout the observation period), try something like the followingto startwith: xi3 i.treatment_group*i.age_group*i.sex*i.observation_interval xtmixed response _I* || patient_id: , nolrtest variance remlYou'll need to install the user-written command, -xi3-, from SSC ifyou haven'talready. Joseph Coveney * * 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/ * * 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/

* * 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/

**References**:**st: Covariates in ANOVAs***From:*Miss Gina Micke <[email protected]>

**st: RE: Covariates in ANOVAs***From:*"Joseph Coveney" <[email protected]>

**st: RE: RE: Covariates in ANOVAs***From:*Miss Gina Micke <[email protected]>

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