[R-sig-ME] Question about random-effects

[Thierry Onkelinx]

Dear Jorge,

It is more clear when you write the nested random effects explicitly
instead of the shorthand.

m2 has (1 | date) + (1 | date:session) + (1 | date:session:periode)
m22 has (1 | session) + (1 | date:session) + (1 | date:session:periode)

Both models have the same fit but a different parameterization.

See my blog post on this topic
https://www.muscardinus.be/2017/07/lme4-random-effects/

Best regards,

ir. Thierry Onkelinx
Statisticus / Statistician

Vlaamse Overheid / Government of Flanders
INSTITUUT VOOR NATUUR- EN BOSONDERZOEK / RESEARCH INSTITUTE FOR NATURE AND
FOREST
Team Biometrie & Kwaliteitszorg / Team Biometrics & Quality Assurance
thierry.onkelinx using inbo.be
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www.inbo.be

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Op za 4 feb. 2023 om 13:36 schreef Jorge Teixeira <
jorgemmtteixeira using gmail.com>:

> Hi everyone.
>
> Context: Two groups (A and B) performed 30 treatment sessions. Each session
> has 4 periods.
>
> However, the wo groups did the intervention 6-months apart, with no
> overlap.
>
> The model fit of both models is equal, but theoretically, one should make
> more sense.
>
> Q1: Is m2 or m22 that captures this the best?
>
> Q2: the fact that I have fixed effect for group makes the previous question
> irrelevant somehow?
>
> Thanks!
>
>
> m2 <- lmer(dp ~ session + period + group + (1 | id) + (1 | date /  session
> /  period), data = dat_long )
>
> summary(m22)
>
> m22 <- lmer(dp ~ session + period + group + (1 | id) + (1 | session / date
> / period), data = dat_long )
>
> summary(m22)
>
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>
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