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Moderation analysis

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jode's picture
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Joined: 08/21/2015 - 08:02
Moderation analysis

Hi metaSEM users, hi Mike,

I am just wondering if and how to apply a moderator analysis in metaSEM. Can I apply the approach you describe in your book beginning on page 170? I would like to test a moderating effect between two effect sizes by treating one variable as moderator. Or is there any other approach?

Thanks for your help.

Johannes

Mike Cheung's picture
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Joined: 10/08/2009 - 22:37
Hi Johannes, Unfortunately,

Hi Johannes,

Unfortunately, it has not been implemented in metaSEM yet. It can be done in OpenMx as shown in the examples https://courses.nus.edu.sg/course/psycwlm/internet/metaSEMbook/index.html#mediation-and-moderation-models

If you have problems in implementing it in OpenMx, please feel free to post them here.

Mike

jode's picture
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Joined: 08/21/2015 - 08:02
Hi Mike, Thanks for the link.

Hi Mike,

Thanks for the link. I tried to follow the analysis and to specify a moderator analysis for my data set.
I have some questions on that:
- Can I use a correlation matrix as input?
- What about the covariance matrix and number of observations?
- How do i specify the M matrix correctly?

I attached my R file with what I got so far.

Thanks for your help
Johannes

Mike Cheung's picture
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Joined: 10/08/2009 - 22:37
Hi Johannes, A single

Hi Johannes,

A single correlation matrix is not sufficient for modelling the moderating effect between effect sizes. We need to have the effect sizes (y) and their sampling covariance matrices (V) as input; otherwise, we cannot specify the mean structure (M matrix in the RAM specification).

By the way, I wonder whether you are testing something similar to the interaction between x and m on y in regression analysis, e.g., y~x+m+x:m or y~x*m. If this is the case, it is not possible to test the interaction with only a correlation matrix on x, m and y.

Mike

jode's picture
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Joined: 08/21/2015 - 08:02
Hi Mike, well I have the

Hi Mike,

well I have the primary studies' correlation matrices I also use for the TSSEM/three-level analysis. Does it work with these? Or is it too complicated to calculate all covariances matrices first?

Johannes

jode's picture
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Joined: 08/21/2015 - 08:02
Hi Mike, I would like to ask

Hi Mike,

I would like to ask again about the possibilities to perform a moderator analysis in a meta-analysis with MASEM/TSSEM because I am not sure from reading your book.
For example, my sample consists of 3 variables A, B and C and I gathered the correlations between all three variables from studies. Now I would like to examine the effect of A on C and how B is moderating that effect.
Is that possible? What data do I need? Or can I only use study characteristics as moderating variables?

I really appreciate your help on that.
Johannes

Mike Cheung's picture
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Joined: 10/08/2009 - 22:37
Hi Johannes, As far as I

Hi Johannes,

As far as I know, it is not possible to test the moderation with only the correlation matrix among the variables.

Using study characteristics as moderators is well developed in meta-analysis. However, I am not aware of any good methods to address the moderation within the studies. This is an area that may need further attention.

Mike

jode's picture
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Joined: 08/21/2015 - 08:02
Hi Mike, Thanks for you

Hi Mike,

Thanks for you reply. That means that you are always referring to study characteristics as moderators in your book?

Johannes

Mike Cheung's picture
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Joined: 10/08/2009 - 22:37
Hi Johannes, Yes. Mike

Hi Johannes,

Yes.

Mike