@article{ref1,
title="Sample sizes and effect sizes are negatively correlated in meta-analyses: evidence and implications of a publication bias against nonsignificant findings",
journal="Communication monographs",
year="2009",
author="Levine, Tim and Asada, Kelli J. and Carpenter, Chris",
volume="76",
number="3",
pages="286-302",
abstract="Meta-analysis involves cumulating effects across studies in order to qualitatively summarize existing literatures. A recent finding suggests that the effect sizes reported in meta-analyses may be negatively correlated with study sample sizes. This prediction was tested with a sample of 51 published meta-analyses summarizing the results of 3,602 individual studies. The correlation between effect size and sample size was negative in almost 80 percent of the meta-analyses examined, and the negative correlation was not limited to a particular type of research or substantive area. This result most likely stems from a bias against publishing findings that are not statistically significant. The primary implication is that meta-analyses may systematically overestimate population effect sizes. It is recommended that researchers routinely examine the n-r scatter plot and correlation, or some other indication of publication bias and report this information in meta-analyses. KW: Aggression; Media Violence; Violent Video Games<p /><p>Language: en</p>",
language="en",
issn="0363-7751",
doi="10.1080/03637750903074685",
url="http://dx.doi.org/10.1080/03637750903074685"
}