Message-ID: <be0efbb1fbda48cb8a751311920ab1ff@UM-MAIL3214.unimaas.nl>
Date: 2022-01-28T15:54:44Z
From: Wolfgang Viechtbauer
Subject: [R-meta] Difference of difference
In-Reply-To: <CA+TgogrCF_=VB7zhzx2epz+ZsA2t7GbAWPSSBt2=-vUwLhvatA@mail.gmail.com>
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 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