Mike,

I kind of have the same question. What if for a mixed effect model, say
using lme(), how to specify the interaction effect (between a fixed effect
and a random effect)? and where to find the result of the interaction?
Thanks.

Jun

On Thu, Apr 16, 2009 at 12:08 PM, Mike Lawrence <Mike.Lawrence@dal.ca>wrote:

> summary(my_lm) will give you t-values, anova(my_lm) will give you
> (equivalent) F-values. summary() might be preferred because it also
> provides the estimates & SE.
>
> > a=data.frame(dv=rnorm(10),iv1=rnorm(10),iv2=rnorm(10))
> > my_lm=lm(dv~iv1*iv2,a)
> > summary(my_lm)
>
> Call:
> lm(formula = dv ~ iv1 * iv2, data = a)
>
> Residuals:
>    Min      1Q  Median      3Q     Max
> -1.8484 -0.2059  0.1627  0.4623  1.0401
>
> Coefficients:
>            Estimate Std. Error t value Pr(>|t|)
> (Intercept)  -0.4864     0.4007  -1.214    0.270
> iv1           0.8233     0.5538   1.487    0.188
> iv2           0.2314     0.3863   0.599    0.571
> iv1:iv2      -0.4110     0.5713  -0.719    0.499
>
> Residual standard error: 1.017 on 6 degrees of freedom
> Multiple R-squared: 0.3161,     Adjusted R-squared: -0.02592
> F-statistic: 0.9242 on 3 and 6 DF,  p-value: 0.4842
>
> > anova(my_lm)
> Analysis of Variance Table
>
> Response: dv
>          Df Sum Sq Mean Sq F value Pr(>F)
> iv1        1 1.9149  1.9149  1.8530 0.2223
> iv2        1 0.4156  0.4156  0.4021 0.5494
> iv1:iv2    1 0.5348  0.5348  0.5175 0.4990
> Residuals  6 6.2004  1.0334
>
>
> On Thu, Apr 16, 2009 at 10:35 AM, kayj <kjaja27@yahoo.com> wrote:
> >
> > Hi,
> >
> >
> > How can I find the p-value for the F test for the interaction terms in a
> > regression linear model lm ?
> >
> > I appreciate your help
> >
> >
> > --
> > View this message in context:
> http://www.nabble.com/F-test-tp23078122p23078122.html
> > Sent from the R help mailing list archive at Nabble.com.
> >
> > ______________________________________________
> > R-help@r-project.org mailing list
> > https://stat.ethz.ch/mailman/listinfo/r-help
> > PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> > and provide commented, minimal, self-contained, reproducible code.
> >
>
>
>
> --
> Mike Lawrence
> Graduate Student
> Department of Psychology
> Dalhousie University
>
> Looking to arrange a meeting? Check my public calendar:
> http://tr.im/mikes_public_calendar
>
> ~ Certainty is folly... I think. ~
>
> ______________________________________________
> R-help@r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>



-- 
Jun Shen PhD
PK/PD Scientist
BioPharma Services
Millipore Corporation
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