Many Labs 2: Investigating Variation in Replicability Across Samples and Settings

Abstract

We conducted preregistered replications of 28 classic and contemporary published findings, with protocols that were peer reviewed in advance, to examine variation in effect magnitudes across samples and settings. Each protocol was administered to approximately half of 125 samples that comprised 15,305 participants from 36 countries and territories. Using the conventional criterion of statistical significance ( p < .05), we found that 15 (54%) of the replications provided evidence of a statistically significant effect in the same direction as the original finding. With a strict significance criterion ( p < .0001), 14 (50%) of the replications still provided such evidence, a reflection of the extremely high-powered design. Seven (25%) of the replications yielded effect sizes larger than the original ones, and 21 (75%) yielded effect sizes smaller than the original ones. The median comparable Cohen’s ds were 0.60 for the original findings and 0.15 for the replications. The effect sizes were small (< 0.20) in 16 of the replications (57%), and 9 effects (32%) were in the direction opposite the direction of the original effect. Across settings, the Q statistic indicated significant heterogeneity in 11 (39%) of the replication effects, and most of those were among the findings with the largest overall effect sizes; only 1 effect that was near zero in the aggregate showed significant heterogeneity according to this measure. Only 1 effect had a tau value greater than .20, an indication of moderate heterogeneity. Eight others had tau values near or slightly above .10, an indication of slight heterogeneity. Moderation tests indicated that very little heterogeneity was attributable to the order in which the tasks were performed or whether the tasks were administered in lab versus online. Exploratory comparisons revealed little heterogeneity between Western, educated, industrialized, rich, and democratic (WEIRD) cultures and less WEIRD cultures (i.e., cultures with relatively high and low WEIRDness scores, respectively). Cumulatively, variability in the observed effect sizes was attributable more to the effect being studied than to the sample or setting in which it was studied.

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Affiliated Institutions

• Pacific Lutheran University US
• William Paterson University US
• Harvard University US
• University of Potsdam DE
• University of Utah US
• UCLouvain BE
• University of Virginia US
• Université de Poitiers FR
• University of Padua IT
• Yale University US
• Saint Joseph's University US
• Uniwersytet SWPS PL
• Johannes Kepler University of Linz AT
• Virginia Commonwealth University US
• National Taiwan University TW
• University of Toronto CA
• Lurie Children's Hospital US
• San Diego State University US
• Universidad Nacional Autónoma de México MX
• Brooklyn College US
• Duke University US
• University of Amsterdam NL
• Centre National de la Recherche Scientifique FR
• National University of Distance Education ES
• Chinese Academy of Sciences CN
• The University of Queensland AU
• Istanbul Bilgi University TR
• Yaşar University TR
• Pennsylvania State University US
• University of Florida US
• University of Jos NG
• Rochester Institute of Technology US
• Baruch College US
• Loyola University Chicago US
• Czech Academy of Sciences, Institute of Psychology CZ
• Northumbria University GB
• London School of Economics and Political Science GB
• HELP University MY
• Texas A&M University US
• Universidad de Los Andes CO
• WHU – Otto Beisheim School of Management DE
• University of Johannesburg ZA
• University of Hawaiʻi at Mānoa US
• Leibniz Institute for Educational Trajectories DE
• Azusa Pacific University US
• Institute of Ethnology, Academia Sinica TW
• Texas A&M University – San Antonio US
• Middle East Technical University TR
• Shanghai International Studies University CN
• Pontificia Universidad Católica de Chile CL
• Wittenberg University US
• Victim Support GB
• Lund University SE
• University of KwaZulu-Natal ZA
• Wilfrid Laurier University CA
• Prague University of Economics and Business CZ
• Hong Kong University of Science and Technology HK
• United Arab Emirates University AE
• University of Salford GB
• Erasmus University Rotterdam NL
• California State University, San Marcos US
• Ghent University BE
• Universidade de Brasília BR
• Université Grenoble Alpes FR
• Başkent University TR
• Universidad del Desarrollo CL
• The Scarborough Hospital CA
• Mathematica Policy Research US
• University of Hong Kong HK
• Eötvös Loránd University HU
• University of Michigan US
• Allegheny College US
• University of Belgrade RS
• American University of Sharjah AE
• James Madison University US
• The Graduate Center, CUNY US
• Worcester Polytechnic Institute US
• Tilburg University NL
• East Texas A&M University US
• Radboud University Nijmegen NL
• Grand Valley State University US
• University of Lausanne CH
• Eindhoven University of Technology NL
• Foresight Science & Technology (United States) US
• Universidad del Desarrollo del Estado de Puebla MX

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