Dr. Bolker, I'm hoping that I might be able to bother you with a quick question. I am trying to *test whether there is significant temporal variation in the effect of a fixed predictor on my response variable *with a model in which year is specified as a random effect (I have 20 years of data). Currently, I am doing this by fitting an interaction between the fixed effect and the random effect of year as* (1|year:fixed)* (per a recommendation that I saw on RSeek.org at some point and some tips that I have read on this list-serve), and am testing the significance of this random interaction with a LRT (i.e., with a model lacking this interaction). Could you tell me if (a) (1|year:fixed) is the correct way to specify this, and (b) if not, do you have a recommendation for how I should specify this interaction to test for temporal variation in the effect of a fixed predictor on my response variable? Thanks.
glmmTMB: testing for temporal variation in effect of fixed predictor on response variable
2 messages · Brenna Levine, Thierry Onkelinx
Dear Brenna, Adding a random effect (1|year:fixed) makes sense, assuming that both year and fixed are discrete. Note that adding this allows for a very liberal temporal variantion by the fixed effect. Each level of the interaction is independent from all other levels. 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 at 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 wo 7 nov. 2018 om 00:16 schreef Brenna Levine <levine.brenna.a at gmail.com
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Dr. Bolker,
I'm hoping that I might be able to bother you with a quick question. I am
trying to *test whether there is significant temporal variation in the
effect of a fixed predictor on my response variable *with a model in which
year is specified as a random effect (I have 20 years of data). Currently,
I am doing this by fitting an interaction between the fixed effect and the
random effect of year as* (1|year:fixed)* (per a recommendation that I saw
on RSeek.org at some point and some tips that I have read on this
list-serve), and am testing the significance of this random interaction
with a LRT (i.e., with a model lacking this interaction).
Could you tell me if (a) (1|year:fixed) is the correct way to specify this,
and (b) if not, do you have a recommendation for how I should specify this
interaction to test for temporal variation in the effect of a fixed
predictor on my response variable?
Thanks.
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