[R-meta] Time as indicator vs time as meaning

[Michael Dewey]

Dear Stefanou

I think it would be find to use the continuous version both as fixed and 
random effect.

Michael

On 09/10/2021 05:49, Stefanou Revesz wrote:
> Dear Meta-Analysis Colleagues,
> 
> We are meta-analyzing 73 longitudinal studies. But we have doubts
> amongst us regarding how to combine the longitudinal effects of these
> studies.
> 
> On the one hand, if we use time only as an indicator of testing
> occasions (pre-test and post-tests), and then use it as fixed and
> random-effect as in:
> 
> rma.mv(es ~ time_id, random = ~ time_id | study, struct = "UN")
> 
> then, we have longitudinally combined apples and oranges. That is,
> time 1 in one study may have covered six months, but time 1 in another
> study may have covered 6 days. This, we think, is problematic in terms
> of the interpretation of both the fixed and random-effects of time.
> 
> So, we have coded for both time_id (testing occasions indicator) and
> time_meaning_wks (length of actual time up to each testing occasion in
> weeks).
> 
> We are wondering how we should incorporate time_meaning_wks into our model?
> 
> Any help is appreciated,
> Stefanou
> 
> study  time_id   time_meaning_wks
> 1        0             0
> 1        1             4
> 1        2             6
> 2        0             0
> 2        1             1
> 
> _______________________________________________
> R-sig-meta-analysis mailing list
> R-sig-meta-analysis using r-project.org
> https://stat.ethz.ch/mailman/listinfo/r-sig-meta-analysis
> 

-- 
Michael
http://www.dewey.myzen.co.uk/home.html