[From the article, “The Meaningfulness of Effect Sizes in Psychological Research: Differences Between Sub-Disciplines and the Impact of Potential Biases” by Thomas Schäfer and Marcus Schwarz, published April 11, 2019 in Frontiers in Psychology]

“From past publications without preregistration, 900 effects were randomly drawn and compared with 93 effects from publications with pre-registration, revealing a large difference: Effects from the former (median r = 0.36) were much larger than effects from the latter (median r = 0.16). That is, certain biases, such as publication bias or questionable research practices, have caused a dramatic inflation in published effects…”

“As we have argued throughout this article, biases in analyzing, reporting, and publishing empirical data (i.e., questionable research practices and publication bias) are most likely responsible for the differences between the effect sizes from studies with and without pre-registration.”

To read the article, click here.

[From the article, “Publication bias examined in meta-analyses from psychology and medicine: A meta-meta-analysis” by Robbie van Aert, Jelte Wicherts, and Marcel van Assen, published April 12, 2019 in PlosONE]

“A large-scale data set was created with meta-analyses published between 2004 and 2014 in Psychological Bulletin and in the Cochrane Library to study the extent and prevalence of publication bias in psychology and medicine…”

“Results of p-uniform suggest that possible overestimation because of publication bias was at most minimal for subsets from Psychological Bulletin.”

“The results of our paper are not in line with previous research…Only weak evidence for the prevalence of publication bias was observed in our large-scale data set of homogeneous subsets of primary studies. No evidence of bias was obtained using the publication bias tests. Overestimation was minimal but statistically significant…”

“Based on these findings in combination with the small percentages of statistically significant effect sizes in psychology and medicine, we conclude that evidence for publication bias in the studied homogeneous subsets is weak, but suggestive of mild publication bias in both disciplines.”

To read the article, click here.