The effect of publication bias on the Q test and assessment of heterogeneity

One of the main goals of meta-analysis is to test for and estimate the heterogeneity of effect sizes. We examined the effect of publication bias on the Q test and assessments of heterogeneity as a function of true heterogeneity, publication bias, true effect size, number of studies, and variation of sample sizes. The present study has two main contributions and is relevant to all researchers conducting meta-analysis. First, we show when and how publication bias affects the assessment of heterogeneity. The expected values of heterogeneity measures H² and I² were analytically derived, and the power and Type I error rate of the Q test were examined in a Monte Carlo simulation study. Our results show that the effect of publication bias on the Q test and assessment of heterogeneity is large, complex, and nonlinear. Publication bias can both dramatically decrease and increase heterogeneity in true effect size, particularly if the number of studies is large and population effect size is small. We therefore conclude that the Q test of homogeneity and heterogeneity measures H² and I² are generally not valid when publication bias is present. Our second contribution is that we introduce a web application, Q-sense, which can be used to determine the impact of publication bias on the assessment of heterogeneity within a certain meta-analysis and to assess the robustness of the meta-analytic estimate to publication bias. Furthermore, we apply Q-sense to 2 published meta-analyses, showing how publication bias can result in invalid estimates of effect size and heterogeneity. (PsycINFO Database Record (c) 2018 APA, all rights reserved)

Quality assessment of scientific manuscripts in peer review and education

We report a vignette study and a survey to investigate which study characteristics influence quality ratings academics give of articles submitted for publication, and academics and students give of students’ theses. In the vignette study, 800 respondents evaluated the quality of an abstract of studies with small or large sample sizes, showing statistically significant or non-significant results, and containing statistical reporting errors or no errors. In the survey, the same participants rated the importance of 29 manuscript characteristics related to the study’s theory, design, conduct, data analyses, and presentation for assessing either the quality of a manuscript or its publishability (article) or grade (thesis). Results showed that quality ratings were affected by sample sizes but not by statistical significance or the presence of statistical reporting errors in the rated researchvignette. These results suggest that researchers’ assessments of manuscript quality are not responsible for publication bias. Furthermore, academics and students provided highly similar ratings of the importance of different aspects relevant to quality assessment of articles and theses. These results suggest that quality criteria for scientific manuscripts are already adopted by students and are similar for submitted manuscripts and theses

Publication bias examined in meta-analyses from psychology and medicine: A meta-meta-analysis

<div><p>Publication bias is a substantial problem for the credibility of research in general and of meta-analyses in particular, as it yields overestimated effects and may suggest the existence of non-existing effects. Although there is consensus that publication bias exists, how strongly it affects different scientific literatures is currently less well-known. We examined evidence of publication bias in a large-scale data set of primary studies that were included in 83 meta-analyses published in Psychological Bulletin (representing meta-analyses from psychology) and 499 systematic reviews from the Cochrane Database of Systematic Reviews (CDSR; representing meta-analyses from medicine). Publication bias was assessed on all homogeneous subsets (3.8% of all subsets of meta-analyses published in Psychological Bulletin) of primary studies included in meta-analyses, because publication bias methods do not have good statistical properties if the true effect size is heterogeneous. Publication bias tests did not reveal evidence for bias in the homogeneous subsets. Overestimation was minimal but statistically significant, providing evidence of publication bias that appeared to be similar in both fields. However, a Monte-Carlo simulation study revealed that the creation of homogeneous subsets resulted in challenging conditions for publication bias methods since the number of effect sizes in a subset was rather small (median number of effect sizes equaled 6). Our findings are in line with, in its most extreme case, publication bias ranging from no bias until only 5% statistically nonsignificant effect sizes being published. These and other findings, in combination with the small percentages of statistically significant primary effect sizes (28.9% and 18.9% for subsets published in Psychological Bulletin and CDSR), led to the conclusion that evidence for publication bias in the studied homogeneous subsets is weak, but suggestive of mild publication bias in both psychology and medicine.</p></div

Heterogeneity in direct replications in psychology and Its association with effect size

We examined the evidence for heterogeneity (of effect sizes) when only minor changes to sample population and settings were made between studies and explored the association between heterogeneity and average effect size in a sample of 68 meta-analyses from 13 preregistered multilab direct replication projects in social and cognitive psychology. Among the many examined effects, examples include the Stroop effect, the "verbal overshadowing" effect, and various priming effects such as "anchoring" effects. We found limited heterogeneity; 48/68 (71%) meta-analyses had nonsignificant heterogeneity, and most (49/68; 72%) were most likely to have zero to small heterogeneity. Power to detect small heterogeneity (as defined by Higgins, Thompson, Deeks, & Altman, 2003) was low for all projects (mean 43%), but good to excellent for medium and large heterogeneity. Our findings thus show little evidence of widespread heterogeneity in direct replication studies in social and cognitive psychology, suggesting that minor changes in sample population and settings are unlikely to affect research outcomes in these fields of psychology. We also found strong correlations between observed average effect sizes (standardized mean differences and log odds ratios) and heterogeneity in our sample. Our results suggest that heterogeneity and moderation of effects is unlikely for a 0 average true effect size, but increasingly likely for larger average true effect size

A many-analysts approach to the relation between religiosity and well-being

The relation between religiosity and well-being is one of the most researched topics in the psychology of religion, yet the directionality and robustness of the effect remains debated. Here, we adopted a many-analysts approach to assess the robustness of this relation based on a new cross-cultural dataset (N = 10, 535 participants from 24 countries). We recruited 120 analysis teams to investigate (1) whether religious people self-report higher well-being, and (2) whether the relation between religiosity and self-reported well-being depends on perceived cultural norms of religion (i.e., whether it is considered normal and desirable to be religious in a given country). In a two-stage procedure, the teams first created an analysis plan and then executed their planned analysis on the data. For the first research question, all but 3 teams reported positive effect sizes with credible/confidence intervals excluding zero (median reported beta = 0.120). For the second research question, this was the case for 65% of the teams (median reported beta = 0.039). While most teams applied (multilevel) linear regression models, there was considerable variability in the choice of items used to construct the independent variables, the dependent variable, and the included covariates

Autonomy–connectedness, self-construal, and acculturation:Associations with mental health in a multicultural society

The present study investigated the associations between self-construal, acculturation, and autonomy?connectedness, as well as the relations between autonomy?connectedness and psychopathological symptoms, controlling for self-construal and acculturation. Participants were 1,209 Dutch individuals, of whom 693 (57.3%) were immigrants with a non-Western background. Results showed that an independent self-construal was positively associated with self-awareness and capacity for managing new situations, and was negatively associated with sensitivity to others (which are the three components of autonomy?connectedness). Moreover, an interdependent self-construal was negatively associated with self-awareness and capacity for managing new situations, and was positively associated with sensitivity to others. Importantly, the latter associations were similar for both Dutch natives and immigrants, and the associations between acculturation and autonomy?connectedness were small and nonsignificant. Autonomy?connectedness, after controlling for self-construal and acculturation, explained a large amount of additional variance in anxiety (12.7%) and depression (14.1), and a medium amount of additional variance in drive for thinness (3.7%) and bulimia (4.8%). Autonomy?connectedness, thus, seems to be an important construct for people with a Western background, as well as for immigrants with a non-Western background

Detection of data fabrication using statistical tools

Scientific misconduct potentially invalidates findings in many scientific fields. Improved detection of unethical practices like data fabrication is considered to deter such practices. In two studies, we investigated the diagnostic performance of various statistical methods to detect fabricated quantitative data from psychological research. In Study 1, we tested the validity of statistical methods to detect fabricated data at the study level using summary statistics. Using (arguably) genuine data from the Many Labs 1 project on the anchoring effect (k=36) and fabricated data for the same effect by our participants (k=39), we tested the validity of our newly proposed 'reversed Fisher method', variance analyses, and extreme effect sizes, and a combination of these three indicators using the original Fisher method. Results indicate that the variance analyses perform fairly well when the homogeneity of population variances is accounted for and that extreme effect sizes perform similarly well in distinguishing genuine from fabricated data. The performance of the 'reversed Fisher method' was poor and depended on the types of tests included. In Study 2, we tested the validity of statistical methods to detect fabricated data using raw data. Using (arguably) genuine data from the Many Labs 3 project on the classic Stroop task (k=21) and fabricated data for the same effect by our participants (k=28), we investigated the performance of digit analyses, variance analyses, multivariate associations, and extreme effect sizes, and a combination of these four methods using the original Fisher method. Results indicate that variance analyses, extreme effect sizes, and multivariate associations perform fairly well to excellent in detecting fabricated data using raw data, while digit analyses perform at chance levels. The two studies provide mixed results on how the use of random number generators affects the detection of data fabrication. Ultimately, we consider the variance analyses, effect sizes, and multivariate associations valuable tools to detect potential data anomalies in empirical (summary or raw) data. However, we argue against widespread (possible automatic) application of these tools, because some fabricated data may be irregular in one aspect but not in another. Considering how violations of the assumptions of fabrication detection methods may yield high false positive or false negative probabilities, we recommend comparing potentially fabricated data to genuine data on the same topic

Degrees of freedom in planning, running, analyzing, and reporting psychological studies:A checklist to avoid p-hacking

The designing, collecting, analyzing, and reporting of psychological studies entail many choices that are often arbitrary. The opportunistic use of these so-called researcher degrees of freedom aimed at obtaining statistically significant results is problematic because it enhances the chances of false positive results and may inflate effect size estimates. In this review article, we present an extensive list of 34 degrees of freedom that researchers have in formulating hypotheses, and in designing, running, analyzing, and reporting of psychological research. The list can be used in research methods education, and as a checklist to assess the quality of preregistrations and to determine the potential for bias due to (arbitrary) choices in unregistered studies

Associations between lifestyle factors and multidimensional frailty:A cross-sectional study among community-dwelling older people

BACKGROUND: Multidimensional frailty, including physical, psychological, and social components, is associated to disability, lower quality of life, increased healthcare utilization, and mortality. In order to prevent or delay frailty, more knowledge of its determinants is necessary; one of these determinants is lifestyle. The aim of this study is to determine the association between lifestyle factors smoking, alcohol use, nutrition, physical activity, and multidimensional frailty. METHODS: This cross-sectional study was conducted in two samples comprising in total 45,336 Dutch community-dwelling individuals aged 65 years or older. These samples completed a questionnaire including questions about smoking, alcohol use, physical activity, sociodemographic factors (both samples), and nutrition (one sample). Multidimensional frailty was assessed with the Tilburg Frailty Indicator (TFI). RESULTS: Higher alcohol consumption, physical activity, healthy nutrition, and less smoking were associated with less total, physical, psychological and social frailty after controlling for effects of other lifestyle factors and sociodemographic characteristics of the participants (age, gender, marital status, education, income). Effects of physical activity on total and physical frailty were up to considerable, whereas the effects of other lifestyle factors on frailty were small. CONCLUSIONS: The four lifestyle factors were not only associated with physical frailty but also with psychological and social frailty. The different associations of frailty domains with lifestyle factors emphasize the importance of assessing frailty broadly and thus to pay attention to the multidimensional nature of this concept. The findings offer healthcare professionals starting points for interventions with the purpose to prevent or delay the onset of frailty, so community-dwelling older people have the possibility to aging in place accompanied by a good quality of life