[R-sig-ME] sample size in glmer model

Souheyla GHEBGHOUB @ouhey|@@ghebghoub @end|ng |rom gm@||@com
Thu Jan 23 12:03:22 CET 2020


Thank you Thierry,

I was mistaken I have 2968 observations (2 Time × 53 participants × 28
items).

Is that enough for 7 parameters?
Do I have room for more interactions ( i would later do a backward
step-wise regression).

Thank you,
Souheyla

On Thu, 23 Jan 2020 at 10:39, Thierry Onkelinx <thierry.onkelinx using inbo.be>
wrote:

> Dear Souheyla,
>
> Your fixed effects need 4 parameters: intercept, V1, TimeLevel2 and
> V1:TimeLevel2
> (Time|Participant) needs 3 parameters: variance of TimeLevel1, variance of
> TimeLevel2 and their covariance.
> The same goes for (Time|Item).
> So you're using 10 parameters.
>
> (Time|Participant) tries to estimate the difference between two times for
> each participant. Such random effect requires much more information than
> (1|Participant). In this case I'd recommended that you have 10 or more
> observations for the majority of the Time/Participant combinations.
>
> Best regards,
>
> ir. Thierry Onkelinx
> Statisticus / Statistician
>
> Vlaamse Overheid / Government of Flanders
> INSTITUUT VOOR NATUUR- EN BOSONDERZOEK / RESEARCH INSTITUTE FOR NATURE AND
> FOREST
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> thierry.onkelinx using inbo.be
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>
>
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>
> Op do 23 jan. 2020 om 11:15 schreef Souheyla GHEBGHOUB <
> souheyla.ghebghoub using gmail.com>:
>
>> Morning Ben,
>>
>> I am not doing (item|Participant).
>> V1 is a duration (continuous) , I should have an interaction of Time of
>> two
>> levels  :  score ~ V1*Time + (Time|Participant) + (Time|item) ,
>> This means I have 7 parameters including intercept (4 random effects +
>> intercept + V1 + TimeLevel1).
>> I have 1484 observations and 53 participants.  The rule is 10 per
>> parameter.
>>
>> My question: Is it 10 participants per parameter (i.e. I am allowed 5
>> parameters) or 10 observation per parameter (I am allowed 148
>> parameters!!!)
>> I guess it is likely per participant, and if its the case, then should I
>> still report results even the power is less (53 divided by 7 = I have 7.5
>> participants per parameter, not 10 as recommended)
>>
>> Thats all
>> Thank you,
>> Souheyla
>>
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>>
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