[R-sig-ME] Grouping variables technically suitable for modeling

[Timothy MacKenzie]

Dear Thierry,

That "As ID2 defines almost the same grouping as ID1, it doesn't make
sense to include both of them in the model." makes good sense.

Thanks!
Tim M

On Tue, Nov 9, 2021 at 9:03 AM Thierry Onkelinx
<thierry.onkelinx using inbo.be> wrote:
>
> Dear Timothy,
>
> I would expect in your example that the combined effect of ID1 and ID2 will be more or less equally split over ID1 and ID2. As this would yield a lower penalty then attributing the effect fully to either ID1 or ID2. Hence the random effect variances of 1|ID1/ID2 will be a lot smaller than 1|ID1 or 1|ID2.
>
> As ID2 defines almost the same grouping as ID1, it doesn't make sense to include both of them in the model.
>
> I have no reference at hand for this. Just common sense.
>
> ir. Thierry Onkelinx
> Statisticus / Statistician
>
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>
> Op di 9 nov. 2021 om 15:19 schreef Timothy MacKenzie <fswfswt using gmail.com>:
>>
>> Dear Ben,
>>
>> Thank you for sharing the references regarding my first question.
>>
>> Regarding my second question, I simply mean if we have say ID1 and ID2,
>> then for ID2 to be distinguishably nested in ID1, it needs to have a
>> different unique categories relative to those of ID1.
>>
>> For example, if ID1 has 120 unique categories and ID2 has 130
>> unique categories nested in ID1, then the variance components for ID1 and
>> ID2 are not distinguishable from each other. As a result, only one of them
>> can be added as a random effect; either (1 | ID1) or (1 | |ID2), but not (1
>> | ID1/ID2).
>>
>> Is this correct and is there a published reference confirming or
>> disconfirming this?
>>
>> Thanks,
>> Tim M
>>
>> On Mon, Nov 8, 2021 at 7:35 PM Ben Bolker <bbolker using gmail.com> wrote:
>>
>> >
>> >     This is a bit of a "how long is a piece of string" question ...
>> >
>> >
>> >    The "5-6 levels of a grouping variable" rule of thumb is quoted in
>> > various places: a variety of those references (Gelman and Hill 2006,
>> > Kéry and Royle 2015, Harrison et al 2018, Arnqvist 2020) are collected
>> > by Gomes
>> > (https://www.biorxiv.org/content/10.1101/2021.04.11.439357v2.full).
>> >
>> >    I sort of see what you mean by your second paragraph, but can you
>> > give an example?
>> >
>> >
>> > On 11/7/21 5:20 PM, Timothy MacKenzie wrote:
>> > > Dear Experts,
>> > >
>> > > Apologies if this question has come up before. But I'm looking for
>> > > published references that provide guidance on when one or more grouping
>> > > variables that theoretically need to be random factors can also
>> > > "technically" be used as random factors?
>> > >
>> > > For example, I have heard for a grouping variable to be technically taken
>> > > as a random factor, it needs to have at least 10 or so unique categories?
>> > > (Any reference to confirm or disconfirm this?)
>> > >
>> > > For example, I have heard for two grouping variables to be technically
>> > > taken as random factors, they each need to have a sufficiently different
>> > > number of unique categories relative to the other one. Otherwise, their
>> > > variance components can't be distinguished from one another and thus only
>> > > one of them can be taken as random, not both (Any reference to confirm or
>> > > disconfirm this?)
>> > >
>> > > Thanks,
>> > > Tim M
>> > >
>> > >       [[alternative HTML version deleted]]
>> > >
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>> > >
>> >
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