Statistical Models for the Meta-analysis of Nonindependent Data

2013 ◽  
Author(s):  
Kerrie Mengersen ◽  
Michael D. Jennions ◽  
Christopher H. Schmid
Keyword(s):  
Statistical Models ◽  
Single Case ◽  
Meta Analysis ◽  
Dry Weight ◽  
Multiple Treatments ◽  
The Individual ◽  
Meta Analyses ◽  
Size Estimates ◽  
Over Time

In many meta-analyses, independence is questionable because there are several effect estimates per study and/or some of the individual studies included in the meta-analysis might not provide independent estimates of the effect. Within-study nonindependence can arise due to multiple measures of the same effect on the same experimental units being made over time, multiple treatments being compared to the same set of control individuals, or different measures being taken (e.g., plant height, dry weight, and photosynthesis rate) from the same experimental units to generate several different effect size estimates. This chapter discusses nonindependence among effect sizes both within and among studies. It focuses on four commonplace situations where nonindependence can occur in ecology and evolution meta-analyses. Each of these four situations is illustrated with a single case study.

The Orchard Plot: Cultivating a Forest Plot for Use in Ecology, Evolution and Beyond

2019 ◽  
Author(s):  
Shinichi Nakagawa ◽  
Malgorzata Lagisz ◽  
Rose E O'Dea ◽  
Joanna Rutkowska ◽  
Yefeng Yang ◽  
...  
Keyword(s):  
Meta Analysis ◽  
R Package ◽  
Effect Sizes ◽  
Forest Plot ◽  
Point Estimates ◽  
Aggregate Effect ◽  
The Individual ◽  
Meta Analyses ◽  
Heterogeneous Effect ◽  
Intuitive Interpretation

‘Classic’ forest plots show the effect sizes from individual studies and the aggregate effect from a meta-analysis. However, in ecology and evolution meta-analyses routinely contain over 100 effect sizes, making the classic forest plot of limited use. We surveyed 102 meta-analyses in ecology and evolution, finding that only 11% use the classic forest plot. Instead, most used a ‘forest-like plot’, showing point estimates (with 95% confidence intervals; CIs) from a series of subgroups or categories in a meta-regression. We propose a modification of the forest-like plot, which we name the ‘orchard plot’. Orchard plots, in addition to showing overall mean effects and CIs from meta-analyses/regressions, also includes 95% prediction intervals (PIs), and the individual effect sizes scaled by their precision. The PI allows the user and reader to see the range in which an effect size from a future study may be expected to fall. The PI, therefore, provides an intuitive interpretation of any heterogeneity in the data. Supplementing the PI, the inclusion of underlying effect sizes also allows the user to see any influential or outlying effect sizes. We showcase the orchard plot with example datasets from ecology and evolution, using the R package, orchard, including several functions for visualizing meta-analytic data using forest-plot derivatives. We consider the orchard plot as a variant on the classic forest plot, cultivated to the needs of meta-analysts in ecology and evolution. Hopefully, the orchard plot will prove fruitful for visualizing large collections of heterogeneous effect sizes regardless of the field of study.

scholarly journals A Statistical Method for Synthesizing Meta-Analyses

2013 ◽  
Vol 2013 ◽  
pp. 1-9 ◽  
Author(s):  
Liansheng Larry Tang ◽  
Michael Caudy ◽  
Faye Taxman
Keyword(s):  
Statistical Method ◽  
Effect Size ◽  
Meta Analysis ◽  
Effect Sizes ◽  
Weighted Mean ◽  
Summary Effect ◽  
Different Types ◽  
Meta Analyses ◽  
Size Estimates ◽  
Similar Search

Multiple meta-analyses may use similar search criteria and focus on the same topic of interest, but they may yield different or sometimes discordant results. The lack of statistical methods for synthesizing these findings makes it challenging to properly interpret the results from multiple meta-analyses, especially when their results are conflicting. In this paper, we first introduce a method to synthesize the meta-analytic results when multiple meta-analyses use the same type of summary effect estimates. When meta-analyses use different types of effect sizes, the meta-analysis results cannot be directly combined. We propose a two-step frequentist procedure to first convert the effect size estimates to the same metric and then summarize them with a weighted mean estimate. Our proposed method offers several advantages over existing methods by Hemming et al. (2012). First, different types of summary effect sizes are considered. Second, our method provides the same overall effect size as conducting a meta-analysis on all individual studies from multiple meta-analyses. We illustrate the application of the proposed methods in two examples and discuss their implications for the field of meta-analysis.

Three stages of entrepreneurial orientation: the founder’s role

2019 ◽  
Vol 26 (2) ◽  
pp. 285-306 ◽  
Author(s):  
Torbjörn Ljungkvist ◽  
Börje Boers ◽  
Joachim Samuelsson
Keyword(s):  
Entrepreneurial Orientation ◽  
Single Case ◽  
Annual Reports ◽  
Structured Interviews ◽  
Theoretical Understanding ◽  
Content Type ◽  
Five Dimensions ◽  
The Impact ◽  
Over Time

Purpose The purpose of this paper is to understand the development of the five dimensions of entrepreneurial orientation (EO) over time by taking a founder’s perspective. Design/methodology/approach The paper draws on an in-depth single-case study. It combines semi-structured interviews in the company with archival data, such as annual reports, press clips and interviews in business magazines. Findings The results indicate that the EO dimensions change from being personalized and directly solution-oriented to being intangible value-creation-oriented. Originality/value By suggesting ownership-based EO configurations, this study contributes insights into how different ownership forms propel EO. These configurations – that is, personal, administrative based and intangible focused – show the impact of the EO dimensions and provide a systematic and theoretical understanding of EO change over time.

A Simple, Principled Approach to Combining Evidence From Meta-Analysis and High-Quality Replications

2018 ◽  
Vol 1 (2) ◽  
pp. 174-185 ◽  
Author(s):  
Evan C. Carter ◽  
Michael E. McCullough
Keyword(s):  
Meta Analysis ◽  
Ego Depletion ◽  
Practical Significance ◽  
High Quality ◽  
Questionable Research Practices ◽  
Combining Evidence ◽  
Meta Analyses ◽  
Work Done ◽  
Combining Information

Recent discussions of the influence of publication bias and questionable research practices on psychological science have increased researchers’ interest in both bias-correcting meta-analytic techniques and preregistered replication. Both approaches have their strengths: For example, meta-analyses can quantitatively characterize the full body of work done in the field of interest, and preregistered replications can be immune to bias. Both approaches also have clear weaknesses: Decisions about which meta-analytic estimates to interpret tend to be controversial, and replications can be discounted for failing to address important methodological heterogeneity. Using the experimental literature on ego depletion as a case study, we illustrate a principled approach to combining information from meta-analysis with information from subsequently conducted high-quality replications. This approach (a) compels researchers to explicate their beliefs in meta-analytic conclusions (and also, when controversy arises, to defend the basis for those beliefs), (b) encourages consideration of practical significance, and (c) facilitates the process of planning replications by specifying the sample sizes necessary to have a reasonable chance of changing the minds of other researchers.

scholarly journals Pearls for Interpreting Neurosurgical Systematic Reviews and Meta-Analyses: Lessons From a Collaborative Effort

Neurosurgery ◽  
2020 ◽  
Vol 87 (3) ◽  
pp. 435-441 ◽  
Author(s):  
Victor M Lu ◽  
Christopher S Graffeo ◽  
Avital Perry ◽  
Michael J Link ◽  
Fredric B Meyer ◽  
...  
Keyword(s):  
Systematic Reviews ◽  
Evidence Based Medicine ◽  
Lessons Learned ◽  
Evidence Based ◽  
Cranial Neuralgia ◽  
The Individual ◽  
Meta Analyses ◽  
Based Medicine ◽  
Over Time

Abstract Systematic reviews and meta-analyses in the neurosurgical literature have surged in popularity over the last decade. It is our concern that, without a renewed effort to critically interpret and appraise these studies as high or low quality, we run the risk of the quality and value of evidence-based medicine in neurosurgery being misinterpreted. Correspondingly, we have outlined 4 major domains to target in interpreting neurosurgical systematic reviews and meta-analyses based on the lessons learned by a collaboration of clinicians and academics summarized as 4 pearls. The domains of (1) heterogeneity, (2) modeling, (3) certainty, and (4) bias in neurosurgical systematic reviews and meta-analyses were identified as aspects in which the authors’ approaches have changed over time to improve robustness and transparency. Examples of how and why these pearls were adapted were provided in areas of cranial neuralgia, spine, pediatric, and neuro-oncology to demonstrate how neurosurgical readers and writers may improve their interpretation of these domains. The incorporation of these pearls into practice will empower neurosurgical academics to effectively interpret systematic reviews and meta-analyses, enhancing the quality of our evidence-based medicine literature while maintaining a critical focus on the needs of the individual patients in neurosurgery.

scholarly journals The Effect of Bilingualism on Older Adults’ Inhibitory Control: A Meta-Analysis

2019 ◽  
Author(s):  
Bonnie A Armstrong ◽  
Natalie Ein ◽  
Brenda I Wong ◽  
Sara N Gallant ◽  
Lingqian Li
Keyword(s):  
Older Adults ◽  
Second Language Acquisition ◽  
Inhibitory Control ◽  
Language Proficiency ◽  
Meta Analysis ◽  
Individual Characteristics ◽  
Bilingual Advantage ◽  
The Individual ◽  
Meta Analyses ◽  
Design And Methods

AbstractBackground and ObjectivesThe effect bilingualism has on older adults’ inhibitory control has been extensively investigated, yet there is continued controversy regarding whether older adult bilinguals show superior inhibitory control compared with monolinguals. The objective of the current meta-analysis was to examine the reliability and magnitude of the bilingualism effect on older adults’ inhibitory control as measured by the Simon and Stroop tasks. In addition, we examined whether individual characteristics moderate the bilingual advantage in inhibition, including age (young–old vs old–old), age of second language acquisition, immigrant status, language proficiency, and frequency of language use.Research Design and MethodsA total of 22 samples for the Simon task and 14 samples for the Stroop task were derived from 28 published and unpublished articles (32 independent samples, with 4 of these samples using more than 1 task) and were analyzed in 2 separate meta-analyses.ResultsAnalyses revealed a reliable effect of bilingualism on older adults’ performance on the Simon (g = 0.60) and Stroop (g = 0.27) tasks. Interestingly, individual characteristics did not moderate the association between bilingualism and older adults’ inhibitory control.Discussion and ImplicationsThe results suggest there is a bilingual advantage in inhibitory control for older bilinguals compared with older monolinguals, regardless of the individual characteristics previously thought to moderate this effect. Based on these findings, bilingualism may protect inhibitory control from normal cognitive decline with age.

scholarly journals A Meta-Analysis of 46 Studies Identified by the FDA Demonstrates that Soy Protein Decreases Circulating LDL and Total Cholesterol Concentrations in Adults

2019 ◽  
Vol 149 (6) ◽  
pp. 968-981 ◽  
Author(s):  
Sonia Blanco Mejia ◽  
Mark Messina ◽  
Siying S Li ◽  
Effie Viguiliouk ◽  
Laura Chiavaroli ◽  
...  
Keyword(s):  
Total Cholesterol ◽  
Soy Protein ◽  
Ldl Cholesterol ◽  
Meta Analysis ◽  
Controlled Trials ◽  
Heart Health ◽  
Health Claim ◽  
The Individual ◽  
Dose Response Effect ◽  
Meta Analyses

ABSTRACT Background Certain plant foods (nuts and soy protein) and food components (viscous fibers and plant sterols) have been permitted by the FDA to carry a heart health claim based on their cholesterol-lowering ability. The FDA is currently considering revoking the heart health claim for soy protein due to a perceived lack of consistent LDL cholesterol reduction in randomized controlled trials. Objective We performed a meta-analysis of the 46 controlled trials on which the FDA will base its decision to revoke the heart health claim for soy protein. Methods We included the 46 trials on adult men and women, with baseline circulating LDL cholesterol concentrations ranging from 110 to 201 mg/dL, as identified by the FDA, that studied the effects of soy protein on LDL cholesterol and total cholesterol (TC) compared with non-soy protein. Two independent reviewers extracted relevant data. Data were pooled by the generic inverse variance method with a random effects model and expressed as mean differences with 95% CI. Heterogeneity was assessed and quantified. Results Of the 46 trials identified by the FDA, 43 provided data for meta-analyses. Of these, 41 provided data for LDL cholesterol, and all 43 provided data for TC. Soy protein at a median dose of 25 g/d during a median follow-up of 6 wk decreased LDL cholesterol by 4.76 mg/dL (95% CI: −6.71, −2.80 mg/dL, P < 0.0001; I2 = 55%, P < 0.0001) and decreased TC by 6.41 mg/dL (95% CI: −9.30, −3.52 mg/dL, P < 0.0001; I2 = 74%, P < 0.0001) compared with non-soy protein controls. There was no dose–response effect or evidence of publication bias for either outcome. Inspection of the individual trial estimates indicated most trials (∼75%) showed a reduction in LDL cholesterol (range: −0.77 to −58.60 mg/dL), although only a minority of these were individually statistically significant. Conclusions Soy protein significantly reduced LDL cholesterol by approximately 3–4% in adults. Our data support the advice given to the general public internationally to increase plant protein intake. This trial was registered at clinicaltrials.gov as NCT03468127.

scholarly journals Clinical Behavior of Ceramic, Hybrid and Composite Onlays. A Systematic Review and Meta-Analysis

2020 ◽  
Vol 17 (20) ◽  
pp. 7582
Author(s):  
Naia Bustamante-Hernández ◽  
Jose María Montiel-Company ◽  
Carlos Bellot-Arcís ◽  
José Félix Mañes-Ferrer ◽  
María Fernanda Solá-Ruíz ◽  
...  
Keyword(s):  
Systematic Review ◽  
Survival Rate ◽  
Meta Analysis ◽  
Posterior Region ◽  
Publication Date ◽  
Clinical Behavior ◽  
Lower Survival Rate ◽  
Meta Analyses ◽  
Over Time

A systematic review and meta-analysis was performed to analyze the survival of onlay restorations in the posterior region, their clinical behavior according to the material used (ceramic reinforced with lithium disilicate, conventional feldspathic ceramic or reinforced with leucite; hybrid materials and composite), possible complications, and the factors influencing restoration success. The systematic review was based on the preferred reporting items for systematic reviews and meta-analyses (PRISMA) statement, without publication date or language restrictions. An electronic search was made in the PubMed, Scopus, Embase, and Cochrane databases. After discarding duplicate publications and studies that failed to meet the inclusion criteria, the articles were selected based on the population, intervention, comparison, outcome (PICO) question. The following variables were considered in the qualitative and quantitative analyses: restoration survival rate (determined by several clinical parameters), the influence of the material used upon the clinical behavior of the restorations, and the complications recorded over follow-up. A total of 29 articles were selected for the qualitative analysis and 27 for the quantitative analysis. The estimated restoration survival rate was 94.2%. The predictors of survival were the duration of follow-up (beta = −0.001; p = 0.001) and the onlay material used (beta = −0.064; p = 0.028). Composite onlays were associated with a lower survival rate over time. Onlays are a good, conservative, and predictable option for restoring dental defects in the posterior region, with a survival rate of over 90%. The survival rate decreases over time and with the use of composite as onlay material.

scholarly journals Controlling for baseline telomere length biases estimates of the rate of telomere attrition

2019 ◽  
Vol 6 (10) ◽  
pp. 190937 ◽  
Author(s):  
Melissa Bateson ◽  
Dan T. A. Eisenberg ◽  
Daniel Nettle
Keyword(s):  
Measurement Error ◽  
Telomere Length ◽  
Statistical Models ◽  
Meta Analysis ◽  
Regression To The Mean ◽  
Inference Models ◽  
Telomere Attrition ◽  
The Mean ◽  
Invalid Inference ◽  
Over Time

Longitudinal studies have sought to establish whether environmental exposures such as smoking accelerate the attrition of individuals' telomeres over time. These studies typically control for baseline telomere length (TL) by including it as a covariate in statistical models. However, baseline TL also differs between smokers and non-smokers, and telomere attrition is spuriously linked to baseline TL via measurement error and regression to the mean. Using simulated datasets, we show that controlling for baseline TL overestimates the true effect of smoking on telomere attrition. This bias increases with increasing telomere measurement error and increasing difference in baseline TL between smokers and non-smokers. Using a meta-analysis of longitudinal datasets, we show that as predicted, the estimated difference in telomere attrition between smokers and non-smokers is greater when statistical models control for baseline TL than when they do not, and the size of the discrepancy is positively correlated with measurement error. The bias we describe is not specific to smoking and also applies to other exposures. We conclude that to avoid invalid inference, models of telomere attrition should not control for baseline TL by including it as a covariate. Many claims of accelerated telomere attrition in individuals exposed to adversity need to be re-assessed.

Cognitive behaviour therapy with compulsive hoarding: a single case study

2020 ◽  
pp. 1-10
Author(s):  
Aasma Yousaf ◽  
Rukhsana Kausar ◽  
Iram Fatima
Keyword(s):  
Single Case ◽  
Compulsive Hoarding ◽  
Behaviour Therapy ◽  
Research Committee ◽  
Current Case ◽  
Programme Committee ◽  
Cognitive Behaviour ◽  
The Individual ◽  
The University

Abstract The current case study used cognitive behaviour treatment (CBT) for the management of a 35-year-old, married man who presented with complaint of compulsive hoarding. The complaint of compulsive hoarding (excessive acquisition, difficulty in discarding saved material and cluttering) was accompanied by feeling of anger, sad mood, low confidence, decreased sleep and appetite, poor problem solving ability, indecisiveness and interpersonal conflicts. The study was approved by the institutional research committee (Departmental Doctoral Programme Committee) and followed by the university research committee (Advance Studies and Review Board) as academic requirement for the duration of 2013-2020. Written consent was also taken from the individual to publish the results of the case. Twenty-eight CBT sessions of one-hour duration were conducted, over a period of six months. Continuous...  

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