[R-meta] Difference of difference

[Stefanou Revesz]

Thank you so much, Wolfgang. I must admit that I failed at achieving
this on my own. In my model below, I want to test:
(coef 4 - coef 1) - (coef 5 - coef 2)

Would that be possible either in anova.rma() or in clubSandwich::Wald_test()?

dd <- read.csv("https://raw.githubusercontent.com/fpqq/w/main/1.csv")
dd$obs <- 1:nrow(dd)

res <- rma.mv(gi ~ 0 + teaching_level:time, vi, random = ~1|study/obs,
data = dd)

Many thanks,
Stefanou

On Fri, Jan 28, 2022 at 9:54 AM Viechtbauer, Wolfgang (SP)
<wolfgang.viechtbauer using maastrichtuniversity.nl> wrote:
>
> Hi Stefanou,
>
> It's certainly something you can do.
>
> anova() can provide a test of such a contrast and predict() will give you the CI.
>
> Best,
> Wolfgang
>
> >-----Original Message-----
> >From: Stefanou Revesz [mailto:stefanourevesz using gmail.com]
> >Sent: Thursday, 27 January, 2022 22:37
> >To: R meta
> >Cc: Viechtbauer, Wolfgang (SP)
> >Subject: Difference of difference
> >
> >Dear Wolfang and the list Members,
> >
> >I've done a post-hoc after my 3-level model. Below is part of the results.
> >
> >At Baseline, elementary was larger than the mixed group by .251 (ignore pval).
> >
> >At post-test1, elementary was larger than the mixed group by .467 (ignore pval).
> >
> >Shall we again subtract the baseline difference from the post-test1
> >difference to better understand the difference between mixed and
> >elementary groups at post-test1?
> >
> >If yes, can we then conduct a test on that difference and get CIs for it?
> >
> >
> >Diff       SE       tval   Df   pval
> >mixed Baseline - elementary Baseline      -0.251   0.277  -0.905   55 0.984
> >mixed Post-test1 - elementary Post-test1  -0.467   0.251  -1.861   55 0.582
> >
> >Thank you so much,
> >Stefanou