[R-meta] Difference of difference

-----Original Message-----
From: Stefanou Revesz [mailto:stefanourevesz at 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