Our new meta-meta-analysis on intelligence research is now online as a preprint at https://psyarxiv.com/ytsvw.
We analyzed 131 meta-analyses in intelligence research to investigate effect sizes, power, and patterns of bias. We find a typical effect of r = .26 and a median sample size of 60.
The median power seems low (see figure below), and we find evidence for small study effects, possibly indicating overestimated effects. We don’t find evidence for a US effect, decline or early-extremes effect, or citation bias.
Comments are very welcome and can be posted on the PubPeer page https://pubpeer.com/publications/9F209A983618EFF9EBED07FDC7A7AC.
Watch a 5 minute interview (in Dutch) in which I explain when replication research is and isn’t useful.
This interview was originally published on the website of Tilburg University:https://www.tilburguniversity.edu/nl/over/schools/socialsciences/nieuws/michele-nuijten-over-de-replication-paradox/
My research and opinions about replications were featured in a three page article in the Dutch national news. Read the full article by Maarten Keulemans here (in Dutch).
Photographs by Adrie Mouthaan.
My latest paper “The replication paradox: Combining studies can decrease accuracy of effect size estimates” is now published in Review of General Psychology. You can find a postprint of the paper here. The full reference is:
Nuijten, M. B., Van Assen, M. A. L. M., Veldkamp, C. L. S., & Wicherts, J. M. (2015).The replication paradox: Combining studies can decrease accuracy of effect size estimates. Review of General Psychology, 19(2), 172-182. http://dx.doi.org/10.1037/gpr0000034
In the latest edition of “De Psychonoom”, the magazine of the Dutch Association for Psychonomy, I talk about the ‘replication paradox’ and explain why replications do not necessarily decrease bias in effect size estimates. Read the interview here (in Dutch).
Will integrating original studies and published replications always improve the reliability of your results? No! Replication studies suffer from the same publication bias as original studies… Read the full blog here.