[R-meta] Computing var-covariance matrix with correlations of six non-independent outcomes
James Pustejovsky
jepu@to @end|ng |rom gm@||@com
Tue Jul 7 22:41:24 CEST 2020
Ha! Following best practice for systematic reviews, a response to your
question has been provided by two coders, working independently. I think
our reliability is pretty decent too.
On Tue, Jul 7, 2020 at 3:33 PM Viechtbauer, Wolfgang (SP) <
wolfgang.viechtbauer using maastrichtuniversity.nl> wrote:
> Dear Mika,
>
> Strictly speaking, the correct way to compute the covariances between
> multiple Cohen's d (or Hedges' g) values would require using methods that
> are described in this chapter:
>
> Gleser, L. J., & Olkin, I. (2009). Stochastically dependent effect sizes.
> In H. Cooper, L. V. Hedges, & J. C. Valentine (Eds.), The handbook of
> research synthesis and meta-analysis (2nd ed., pp. 357–376). New York:
> Russell Sage Foundation.
>
> In particular, equation (19.27) gives the covariance between two d values
> for two different outcomes computed based on the same sample of subjects
> (and we assume that the correlation between the two outcomes is the same
> for subjects in the treatment and the control group). An example
> illustrating an application of this is provided here:
>
>
> http://www.metafor-project.org/doku.php/analyses:gleser2009#multiple-endpoint_studies
>
> although the code for the example is a bit simpler because each study has
> exactly 2 d values.
>
> However, one can take a simpler approach that gives very similar results.
> Namely, if v_1 and v_2 are the sampling variances of d_1 and d_2 and r is
> the correlation between the two outcomes, then r * sqrt(v_1 * v_2) is
> usually a close approximation to what (19.27) would provide.
>
> Based on your example, this can be computed here as follows:
>
> # this is only required because you coded missings as "NA" (and not as NA)
> corlist <- lapply(corlist, function(x) matrix(as.numeric(x), nrow=6,
> ncol=6))
>
> # we only need a correlation matrix for the levels of motivation actually
> observed
> mots <- split(meta$motivation, meta$study)
> corlist <- mapply(function(rmat, mots) R[mots,mots], corlist, mots)
> corlist
>
> Vfun <- function(vi,rmat) {
> if (length(vi) == 1L) {
> matrix(vi)
> } else {
> S <- diag(sqrt(vi))
> S %*% rmat %*% S
> }
> }
>
> V <- mapply(Vfun, split(meta$v, meta$study), corlist)
>
> Now V is the var-cov matrix of your SMD values, so you could proceed with
> a multivariate model with:
>
> res <- rma.mv(g, V, mods = ~ factor(motivation) - 1, random = ~
> factor(motivation) | study, struct="UN", data=meta)
> res
>
> This is a very general model allowing each level of motivation to have its
> own heterogeneity variance component and each pair to have its own
> correlation. I wouldn't recommend this with only 8 studies, but with 25
> studies, this might be more sensible.
>
> Best,
> Wolfgang
>
> >-----Original Message-----
> >From: Mika Manninen [mailto:mixu89 using gmail.com]
> >Sent: Tuesday, 07 July, 2020 21:53
> >To: James Pustejovsky
> >Cc: Viechtbauer, Wolfgang (SP); r-sig-meta-analysis using r-project.org
> >Subject: Re: [R-meta] Computing var-covariance matrix with correlations of
> >six non-independent outcomes
> >
> >James,
> >
> >Thank you so much for replying.
> >
> >The dataset (8 studies out of 25 included) can be created with the
> following
> >code:
> >
> >###Creating vectors for the outcome, study, motivation, effect size, and
> >variance estimate
> >
> >#Total effects/outcomes
> >outcome <- c(1:28)
> >
> >#Study
> >study <- c(1,1,1,1,1,2,2,2,2,3,3,3,3,3,4,4,4,4,4,5,6,7,8,8,8,8,8,8)
> >
> >#Six different motivation types measured in the studies
> >motivation <-
> >c(1,3,4,5,6,1,3,4,5,1,3,4,5,6,1,3,4,5,6,6,6,6,1,2,3,4,5,6)
> >
> >#Hedges g:s
> >g <- c(0.6068, 0.0603, 0.2684, -0.0886, 0.0415, 1.592, 1.4031, 0.7928,
> >0.2013, 0.541, 0.1169,
> > 0.3129, -0.0275, -0.3536, 1.5886, 2.7218, -1.6273, -0.4375,
> -1.0695,
> >-0.1247, -0.1038,
> > -0.2706, 0.2045, -0.2701, 0.3763, -0.7371, -0.0666, 0.2789)
> >
> >#Variance estimates
> >v <- c( 0.0162, 0.0155, 0.0157, 0.0155, 0.0155, 0.1889,
> >0.17875984,0.15484225,
> > 0.14432401, 0.0329, 0.0318, 0.0322, 0.0318, 0.0323, 0.1886,
> 0.2758,
> > 0.1909, 0.147, 0.164, 0.0067, 0.0028, 0.004, 0.0726, 0.0729,
> 0.0735,
> > 0.0771, 0.0723, 0.073)
> >
> >###Dataset matrix with different levels and motivation types
> >meta <- cbind(outcome, study, motivation, g, v)
> >View(meta)
> >
> >I created 6x6 correlation matrices (with 15 unique correlations) for the
> >eight included studies. I am not sure if this is the most sensible
> approach
> >as only a few studies have measured all six outcomes. Value NA reflects
> the
> >absence of a correlation (absence of that one or both of the motivation
> >types in the study). The row and column numbers (1-6) correspond to the
> >variable motivation in the created dataset.
> >
> >### Correlation matrices for studies 1-8
> >
> >study1c <- rbind(c(1, "NA", .96, .34, -.33, -.66), c("NA", "NA", "NA",
> "NA",
> >"NA", "NA"), c(.96, "NA", 1, .55, -.12, -.50),
> > c(.34, "NA", .55, 1, .53, .05), c(-.33, "NA", -.12, .53,
> 1,
> >.72), c(-.66, "NA", -.50, .05, .72, 1))
> >
> >study2c <- rbind(c(1, "NA", .96, .34, -.33, "NA"), c("NA", "NA", "NA",
> "NA",
> >"NA", "NA"), c(.96, "NA", 1, .55, -.12, "NA"),
> > c(.34, "NA", .55, 1, .53, "NA"), c(-.33, "NA", -.12, .53,
> 1,
> >"NA"), c("NA", "NA", "NA", "NA", "NA", "NA"))
> >
> >study3c <- rbind(c(1, "NA", .96, .34, -.33, -.66), c("NA", "NA", "NA",
> "NA",
> >"NA", "NA"), c(.96, "NA", 1, .55, -.12, -.50),
> > c(.34, "NA", .55, 1, .53, .05), c(-.33, "NA", -.12, .53,
> 1,
> >.72), c(-.66, "NA", -.50, .05, .72, 1))
> >
> >study4c <- rbind(c(1, "NA", .85, .35, .06, -.44), c("NA", "NA", "NA",
> "NA",
> >"NA", "NA"), c(.85, "NA", 1, .59, .46, -.14),
> > c(.35, "NA", .59, 1, .71, .27), c(.06, "NA", .46, .71, 1,
> >.52), c(-.44, "NA", -.14, .27, .52, 1))
> >
> >study5c <- rbind(c("NA", "NA", "NA", "NA", "NA", "NA"), c("NA", "NA",
> "NA",
> >"NA", "NA", "NA"), c("NA", "NA", "NA", "NA", "NA", "NA"),
> > c("NA", "NA", "NA", "NA", "NA", "NA"), c("NA", "NA", "NA",
> >"NA", "NA", "NA"), c("NA", "NA", "NA", "NA", "NA", 1))
> >
> >study6c <- rbind(c("NA", "NA", "NA", "NA", "NA", "NA"), c("NA", "NA",
> "NA",
> >"NA", "NA", "NA"), c("NA", "NA", "NA", "NA", "NA", "NA"),
> > c("NA", "NA", "NA", "NA", "NA", "NA"), c("NA", "NA", "NA",
> >"NA", "NA", "NA"), c("NA", "NA", "NA", "NA", "NA", 1))
> >
> >study7c <- rbind(c("NA", "NA", "NA", "NA", "NA", "NA"), c("NA", "NA",
> "NA",
> >"NA", "NA", "NA"), c("NA", "NA", "NA", "NA", "NA", "NA"),
> > c("NA", "NA", "NA", "NA", "NA", "NA"), c("NA", "NA", "NA",
> >"NA", "NA", "NA"), c("NA", "NA", "NA", "NA", "NA", 1))
> >
> >study8c <- rbind(c(1, .79, .84, .24, -.20, -.50), c(.79, 1, .93, .47,
> .00, -
> >.31), c(.84, .93, 1, .57, -.07, -.52),
> > c(.24, .47, .57, 1, .43, .01), c(-.20, .00, -.07, .43,
> >1, .55), c(-.50, -.31, -.52, .01, .55, 1))
> >
> >#list with all the correlations matrices
> >
> >corlist <- list(study1c, study2c, study3c, study4c, study5c, study6c,
> >study7c, study8c)
> >
> >Mika
> >
> >ti 7. heinäk. 2020 klo 19.54 James Pustejovsky (jepusto using gmail.com)
> >kirjoitti:
> >Hi Mika,
> >
> >To add to Wolfgang's question, could you tell us a little bit more about
> how
> >you have structured the data on correlations between types of motivation?
> Is
> >it just one correlation matrix (6X6 matrix, with 1 + 2 + 3 + 4 + 5 = 15
> >unique correlations)? Or is it study-specific?
> >
> >This sort of calculation is a bit tricky to carry out so I am not
> surprised
> >that you haven't found a solution in the listserv archives. If you are
> >willing to share your dataset (or a subset thereof, say 3-4 studies worth
> of
> >data), it may make it easier for us to help problem solve.
> >
> >James
> >
> >On Tue, Jul 7, 2020 at 11:42 AM Viechtbauer, Wolfgang (SP)
> ><wolfgang.viechtbauer using maastrichtuniversity.nl> wrote:
> >Dear Mika,
> >
> >What effect size measure are you using for the meta-analysis?
> >
> >Best,
> >Wolfgang
> >
> >>-----Original Message-----
> >>From: R-sig-meta-analysis [mailto:r-sig-meta-analysis-bounces using r-
> >project.org]
> >>On Behalf Of Mika Manninen
> >>Sent: Tuesday, 07 July, 2020 18:10
> >>To: r-sig-meta-analysis using r-project.org
> >>Subject: [R-meta] Computing var-covariance matrix with correlations of
> six
> >>non-independent outcomes
> >>
> >>Hello,
> >>
> >>I am doing a meta-analysis looking at the effect of a teaching
> intervention
> >>(versus control) on six types of motivation/behavioral regulation.
> >>Theoretically and empirically these constructs form a continuum in which
> >>the continuum neighbors are most strongly positively correlated and the
> >>furthest from one another most negatively correlated.
> >>
> >>I have 95 effects. These effects come from 25 studies, each reporting
> >>scores for between 1-6 motivation types. The number of effects per
> >>motivation ranges from 22 to 13. In some studies, they have measured only
> >>one or two types whereas in others they have measured 5 or all 6 types of
> >>motivation.
> >>
> >>I originally ran a separate random-effects meta-analysis for all the six
> >>outcomes. However, I got feedback that the dependency of the motivation
> >>types should be taken into account and a 3-level meta-analysis was
> >>recommended. After looking into it, the 3-level model seems to be a worse
> >>approach than the multivariate approach.
> >>
> >>As is not usually the case, I have succeeded in gathering all
> correlations
> >>between all the motivation types for all studies (some from original
> >>reporting and some from previous meta-analysis findings).
> >>
> >>My question is, how do I compute the V-matrix for this data in order to
> run
> >>the multivariate analysis? I read the whole archive but I could not find
> a
> >>clear answer to the problem.
> >>
> >>Thank you very much in advance,
> >>
> >>Mika
>
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