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

[Thierry Onkelinx]

Dear Jorge,

It is hard to give good advice without thorough insight in your case. I
recommend you consult a local statistician.

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
Havenlaan 88 bus 73, 1000 Brussel
www.inbo.be

///////////////////////////////////////////////////////////////////////////////////////////
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
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<https://www.inbo.be>


Op di 7 feb. 2023 om 22:04 schreef Jorge Teixeira <
jorgemmtteixeira using gmail.com>:

> Dear Thierry Onkelin, thanks for the reply.
>
> Do you have an opinion about which model best represents the context I
> have described? That's my main doubt.
>
> Thank you.
>
> Thierry Onkelinx <thierry.onkelinx using inbo.be> escreveu no dia segunda,
> 6/02/2023 à(s) 20:07:
>
>> 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
>> Havenlaan 88 bus 73, 1000 Brussel
>> www.inbo.be
>>
>>
>> ///////////////////////////////////////////////////////////////////////////////////////////
>> 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
>>
>> ///////////////////////////////////////////////////////////////////////////////////////////
>>
>> <https://www.inbo.be>
>>
>>
>> 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)
>>>
>>>         [[alternative HTML version deleted]]
>>>
>>> _______________________________________________
>>> R-sig-mixed-models using r-project.org mailing list
>>> https://stat.ethz.ch/mailman/listinfo/r-sig-mixed-models
>>>
>>

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