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Smaller Effect Sizes (smaller + effect_size)

Distribution by Scientific Domains

Psychology	50%

Selected Abstracts

Memory distortion in eyewitnesses: a meta-analysis of the post-identification feedback effect

APPLIED COGNITIVE PSYCHOLOGY, Issue 7 2006
Amy Bradfield Douglass
Feedback administered to eyewitnesses after they make a line-up identification dramatically distorts a wide range of retrospective judgements (e.g. G. L. Wells & A. L. Bradfield, 1998 Journal of Applied Psychology, 83(3), 360,376.). This paper presents a meta-analysis of extant research on post-identification feedback, including 20 experimental tests with over 2400 participant-witnesses. The effect of confirming feedback (i.e. ,Good, you identified the suspect') was robust. Large effect sizes were obtained for most dependent measures, including the key measures of retrospective certainty, view and attention. Smaller effect sizes were obtained for so-called objective measures (e.g. length of time the culprit was in view) and comparisons between disconfirming feedback and control conditions. This meta-analysis demonstrates the reliability and robustness of the post-identification feedback effect. It reinforces recommendations for double-blind testing, recording of eyewitness reports immediately after an identification is made, and reconsideration by court systems of variables currently recommended for consideration in eyewitness evaluations. Copyright © 2006 John Wiley & Sons, Ltd. [source]

Depression, depressive symptoms and mortality in persons aged 65 and over living in the community: a systematic review of the literature

INTERNATIONAL JOURNAL OF GERIATRIC PSYCHIATRY, Issue 6 2001
Pedro Saz
Abstract Background No recent attempt has been made to synthesize information on mortality and depression despite the theoretical and practical interest in the topic. Our objective was to estimate in the older population the influence on mortality of depression and depressive symptoms. Methods Data sources were: Medline, Embase, personal files and colleagues' records. Studies were considered if they included a majority of persons aged ,,65 years at baseline either drawn from a total community sample or drawn from a random sample from the community. Samples from healthcare facilities were excluded. Effect sizes were extracted from the papers; if they were not included in the published papers, effect sizes were calculated if possible. No attempt was made to contact authors for missing data. Results We found 21 reports on 23 cohorts using depression diagnosis. For 15 of these, odds ratios were pooled using the Greenland method based on confidence intervals (CIs), giving an estimated odds ratio for mortality with depression of 1.73 (95% CI 1.53 to 1.95). A fixed effects meta-regression of these studies suggested that longer follow-up predicted smaller effect sizes (log odds ratios ,0.096 per year (95% CI ,0.179 to ,0.014)). There is a weak suggestion of a reduced effect of depression on mortality for women. We were unable to pool effect sizes from the 17 studies using symptom totals and scales, or from eight studies of specific symptoms. Conclusions The studies show that diagnosed depression in community-resident older people is associated with increased mortality. The picture for sex differences is still unclear. Copyright © 2001 John Wiley & Sons, Ltd. [source]

Publication bias in ecology and evolution: an empirical assessment using the ,trim and fill' method

BIOLOGICAL REVIEWS, Issue 2 2002
MICHAEL D. JENNIONS
ABSTRACT Recent reviews of specific topics, such as the relationship between male attractiveness to females and fluctuating asymmetry or attractiveness and the expression of secondary sexual characters, suggest that publication bias might be a problem in ecology and evolution. In these cases, there is a significant negative correlation between the sample size of published studies and the magnitude or strength of the research findings (formally the ,effect size'). If all studies that are conducted are equally likely to be published, irrespective of their findings, there should not be a directional relationship between effect size and sample size; only a decrease in the variance in effect size as sample size increases due to a reduction in sampling error. One interpretation of these reports of negative correlations is that studies with small sample sizes and weaker findings (smaller effect sizes) are less likely to be published. If the biological literature is systematically biased this could undermine the attempts of reviewers to summarise actual biology relationships by inflating estimates of average effect sizes. But how common is this problem? And does it really effect the general conclusions of literature reviews? Here, we examine data sets of effect sizes extracted from 40 peer-reviewed, published meta-analyses. We estimate how many studies are missing using the newly developed ,trim and fill' method. This method uses asymmetry in plots of effect size against sample size (,funnel plots') to detect ,missing' studies. For random-effect models of meta-analysis 38% (15/40) of data sets had a significant number of ,missing' studies. After correcting for potential publication bias, 21% (8/38) of weighted mean effects were no longer significantly greater than zero, and 15% (5/34) were no longer statistically robust when we used random-effects models in a weighted meta-analysis. The mean correlation between sample size and the magnitude of standardised effect size was also significantly negative (rs=-0.20, P < 0-0001). Individual correlations were significantly negative (P < 0.10) in 35% (14/40) of cases. Publication bias may therefore effect the main conclusions of at least 15,21% of meta-analyses. We suggest that future literature reviews assess the robustness of their main conclusions by correcting for potential publication bias using the ,trim and fill' method. [source]

Hostile Attribution of Intent and Aggressive Behavior: A Meta-Analysis

CHILD DEVELOPMENT, Issue 3 2002
Bram Orobio De Castro
A meta-analytic review was conducted to explain divergent findings on the relation between children's aggressive behavior and hostile attribution of intent to peers. Forty-one studies with 6,017 participants were included in the analysis. Ten studies concerned representative samples from the general population, 24 studies compared nonaggressive to extremely aggressive nonreferred samples, and 7 studies compared nonreferred samples with children referred for aggressive behavior problems. A robust significant association between hostile attribution of intent and aggressive behavior was found. Effect sizes differed considerably between studies. Larger effects were associated with more severe aggressive behavior, rejection by peers as one of the selection criteria, inclusion of 8- to-12-year-old participants, and absence of control for intelligence. Video and picture presentation of stimuli were associated with smaller effect sizes than was audio presentation. Staging of actual social interactions was associated with the largest effects. The importance of understanding moderators of effect size for theory development is stressed. [source]