degree of freedom is non-integer from lmerTest
Yuqi, By default, the DFs in lmerTest are based on the Satterthwaite approximation: https://en.wikipedia.org/wiki/Welch%E2%80%93Satterthwaite_equation Also see ?lmerTest::summary.merModLmerTest Jake
On Thu, Oct 5, 2017 at 4:59 PM, Yuqi Liu <yliu at psych.udel.edu> wrote:
Dear R-experts,
I am using lmerTest to do mixed model analysis on one of my experiments.
There are two factors, each with 2 levels, resulting in 4 experiment
conditions. It was repeated measures design, and each experiment condition
was conducted once for each individual. The model is thus very simple, with
each factor as a fixed effect and subjects as a random effect: model <-
lmerTest (DV~IV1*IV2+(1|subject),data).
When I looked at the result using summary(model), the Dfs are
non-integers, is it because we had to exclude some of the trials, so that
some participants had missing data? In general, I am wondering how t-tests
are performed in lmerTest, and how degree of freedom was calculated.
Thank you for your help!
Yuqi
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