[R-meta] Question about running a completely "within study" meta analysis

Kate Humphreys k@humphrey@ @end|ng |rom v@nderb||t@edu
Tue Jan 22 18:57:24 CET 2019

We would like to conduct a "within study" meta-analysis. Briefly, we have
been following a group of children who, at infancy, were randomly assigned
to a high-quality foster care or to care as usual. In addition to a
baseline assessment, children were again assessed in waves at 30, 42, and
54 months, and at 8, 12, and 16 years. The assessments include a large
number of domains and a number of different types of information sources.
In other words, we want to determine the average "effect" of the
intervention across all outcomes and, of course, whether aspects of the
measurement, assessment wave, or domain might moderate these effects. Only
participants from this single study would be included, and all measurements
are known.

The issue we have run into is with regards to the variance structure.
Specifically, we initially envisioned a multi-level meta-analysis similar
to the example by Konstantopoulos (2011) posted on your website (
http://www.metafor-project.org/doku.php/analyses:konstantopoulos2011) with
a structure similar to this (prior to testing moderators):

model1 <- rma(
   random = 1 | wave/domain
   method = "REML",
   data = df

However, because we wish to estimate the average true effect across waves
and domains for the same individuals, I believe we would be violating the
assumption that the sampling errors of the effect size estimates are
independent. Therefore, we also considered the Berkey et al. (1998) example
(http://www.metafor-project.org/doku.php/analyses:berkey1998); however, it
isn't clear to us whether this would apply to our special case given that
this example deals with multiple outcomes assessed within multiple studies.
We aren't sure how we would calculate the covariances of our observed
effects when we have effect sizes from a single group of individuals nested
within waves rather studies.

Thank you for considering this request for guidance.

Kathryn L. Humphreys, Ph.D., Ed.M.
Assistant Professor
Department of Psychology and Human Development
Vanderbilt University, Peabody College
230 Appleton Place #552
Hobbs Building 307B
Nashville, TN 37203
P: 615/343-0379
F: 615/343-9494

Director: Stress and Early Adversity (SEA) Lab
Jacobs Foundation Research Fellow, 2018-2020
Member, Vanderbilt Kennedy Center <https://vkc.mc.vanderbilt.edu/vkc/>

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