[R-sig-ME] interactions lmer continuous and categorical fixed factor

[Thierry Onkelinx]

Dear Lotte,

I assume that the "one p-value for the interaction" is the p-value from
anova(model). Note that this tests a different hypothesis than the
hypothesis than summary(model) tests (without reporting p-values).

IMHO, p-values of parameters estimates are not that relevant. Confidence
intervals of those parameter estimates are much more relevant. I'd rather
report those.

Best regards,

ir. Thierry Onkelinx
Instituut voor natuur- en bosonderzoek / Research Institute for Nature and
Forest
team Biometrie & Kwaliteitszorg / team Biometrics & Quality Assurance
Kliniekstraat 25
1070 Anderlecht
Belgium

To call in the statistician after the experiment is done may be no more
than asking him to perform a post-mortem examination: he may be able to say
what the experiment died of. ~ Sir Ronald Aylmer Fisher
The plural of anecdote is not data. ~ Roger Brinner
The combination of some data and an aching desire for an answer does not
ensure that a reasonable answer can be extracted from a given body of data.
~ John Tukey

2015-06-01 16:56 GMT+02:00 Lotte Schoot <Lotte.Schoot op mpi.nl>:

> Hi,
>
> I am using the lmer function in lme4 to test a model like this:
>
> DV ~ factor1 * factor2 (simplified for purposes of illustration, so
> without random effects structure)
>
> DV = continuous (Reaction time)
> factor1 = continuous
> factor2 = categorical (3 levels)
>
> summary(model) will give me output like this:
>
> factor2-level1 * Factor1 = xxx
> factor2-level2 * Factor1 = xxx
> factor2-level3 * Factor1 = xxx
>
> If I try to get p-values for this model, however, I only get one p-value
> for the interaction factor2 * factor 1.
>
> What do you recommend to report in this case?
> p-values with corresponding F-values and df, or the t-values found in
> summary(model), without any p-values?
>
> Thanks in advance,
> Lotte
>
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