Hi all, I am currently investigating the possibility of assessing non-linear effects in a meta-regression. For example, I am interested in the relationship between risk-taking and performance, and I want to assess whether the mean score of risk taking has a non-linear moderating effect on that relationship. I had a look at Wolfgang?s previous examples on adding restricted cubic splines to mixed effects models via the rms package e.g. https://stats.stackexchange.com/questions/279668/meta-regression-using-restr icted-cubic-splines-with-rma-from-the-metafor-pack?rq=1 https://stat.ethz.ch/pipermail/r-sig-meta-analysis/2018-February/000551.html and looked a bit into Frank Harrell?s book concerning the adequate number and location of nodes. My question now is, how do I determine/test whether the plotted spline is actually significant/meaningful? I am a bit unsure what I should make of the mixed effects model results in that regard or if I have to perform additional tests. Best Jens -------------- next part -------------- An HTML attachment was scrubbed... URL: <https://stat.ethz.ch/pipermail/r-sig-meta-analysis/attachments/20180424/e12d9b1d/attachment.html> -------------- next part -------------- A non-text attachment was scrubbed... Name: smime.p7s Type: application/pkcs7-signature Size: 7675 bytes Desc: not available URL: <https://stat.ethz.ch/pipermail/r-sig-meta-analysis/attachments/20180424/e12d9b1d/attachment.p7s>
[R-meta] Question regarding non-linear effects in meta-regression
2 messages · Jens Schüler, Michael Dewey
Dear Jens Comments in line
On 24/04/2018 12:38, Jens Sch?ler wrote:
Hi all, I am currently investigating the possibility of assessing non-linear effects in a meta-regression. For example, I am interested in the relationship between risk-taking and performance, and I want to assess whether the mean score of risk taking has a non-linear moderating effect on that relationship. I had a look at Wolfgang?s previous examples on adding restricted cubic splines to mixed effects models via the rms package e.g. https://stats.stackexchange.com/questions/279668/meta-regression-using-restricted-cubic-splines-with-rma-from-the-metafor-pack?rq=1 https://stat.ethz.ch/pipermail/r-sig-meta-analysis/2018-February/000551.html and looked a bit into Frank Harrell?s book concerning the adequate number and location of nodes. My question now is, how do I determine/test whether the plotted spline is actually significant/meaningful?
I would suggest that looking at the plot as suggested in the examples to which you link is the best way to visualise and explain to others what exactly is going on with your moderator. If you want a formal test then comparing a model with and without the spline using anova() would seem the way to go.
I am a bit unsure what I should make of the mixed effects model results in that regard or if I have to perform additional tests. Best Jens
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