grad-meta-analysis

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後設分析 (Meta-Analysis)

元分析 (Meta-Analysis)

Overview

概述

Meta-analysis statistically combines effect sizes from multiple independent studies to produce a pooled estimate with greater precision and generalizability. It quantifies between-study heterogeneity and tests for publication bias, providing a rigorous evidence synthesis that goes beyond narrative literature reviews.
元分析通过统计学方法整合多项独立研究的效应量,生成合并估计值,具备更高的精确性和普适性。它量化研究间的异质性并检验发表偏倚,提供了比叙述性文献综述更严谨的证据整合方式。

When to Use

适用场景

  • Synthesizing quantitative findings from multiple studies on the same research question
  • Resolving conflicting results across studies
  • Estimating an overall effect size with tighter confidence intervals
  • Identifying moderators that explain heterogeneity across studies
  • 针对同一研究问题,整合多项研究的量化结果
  • 解决不同研究间的结果冲突
  • 估计具有更窄置信区间的整体效应量
  • 识别可解释研究间异质性的调节变量

When NOT to Use

不适用场景

  • Studies are too heterogeneous in constructs, measures, or populations to combine meaningfully
  • Fewer than 5 studies are available (pooled estimates become unreliable)
  • Primary studies have fundamentally different research designs (mixing RCTs with observational)
  • The research question is qualitative or conceptual rather than quantitative
  • 研究在概念、测量方法或研究人群上差异过大,无法进行有意义的整合
  • 可用研究数量少于5项(合并估计值会变得不可靠)
  • 原始研究的设计存在本质差异(如将随机对照试验与观察性研究混合)
  • 研究问题为定性或概念性,而非定量

Assumptions

假设前提

IRON LAW: A meta-analysis is only as good as the studies it includes —
garbage in, garbage out. Publication bias inflates pooled effect sizes
because non-significant findings go unpublished.
Key assumptions:
  1. Studies estimate the same underlying construct (conceptual homogeneity)
  2. Effect sizes are statistically independent (one effect per study, or use multilevel models)
  3. Study-level moderators are coded reliably and without bias
  4. The search strategy captures the relevant population of studies (no systematic omission)
铁律:元分析的质量取决于纳入研究的质量——输入垃圾,输出垃圾。发表偏倚会夸大合并效应量,因为无显著性结果的研究往往不会被发表。
核心假设:
  1. 所有研究均估计同一潜在概念(概念同质性)
  2. 效应量在统计学上相互独立(每项研究仅提取一个效应量,或使用多水平模型)
  3. 研究层面的调节变量编码可靠且无偏倚
  4. 检索策略覆盖了相关研究群体(无系统性遗漏)

Methodology

方法流程

Step 1 — Extract and Code Effect Sizes

步骤1 — 提取并编码效应量

Convert study findings to a common effect size metric (Cohen's d, Hedges' g, r, OR). Code study-level moderators (sample size, design, context). See
references/
for conversion formulas.
将研究结果转换为通用的效应量指标(Cohen's d、Hedges' g、r、OR)。编码研究层面的调节变量(样本量、研究设计、研究场景)。转换公式可参考
references/
目录。

Step 2 — Choose Fixed-Effect vs Random-Effects Model

步骤2 — 选择Fixed-effect模型 vs Random-effects模型

Fixed-effect assumes one true effect; random-effects assumes effects vary across studies. If studies span different populations or contexts, random-effects is almost always appropriate.
Fixed-effect模型假设存在唯一真实效应;Random-effects模型假设效应在不同研究间存在差异。若研究涵盖不同人群或场景,Random-effects模型几乎总是更合适的选择。

Step 3 — Assess Heterogeneity

步骤3 — 评估异质性

Compute Q statistic (test of homogeneity), I² (proportion of variance due to heterogeneity), and τ² (between-study variance). I² > 75% indicates substantial heterogeneity warranting moderator analysis.
计算Q统计量(同质性检验)、I²(异质性导致的方差占比)和τ²(研究间方差)。I² > 75%表明存在显著异质性,需进行调节变量分析。

Step 4 — Test for Publication Bias and Report

步骤4 — 检验发表偏倚并撰写报告

Use funnel plot, Egger's regression test, and trim-and-fill method. Report pooled effect, CI, prediction interval, and results of bias assessment.
使用漏斗图、Egger回归检验和剪补法(trim-and-fill)。报告合并效应量、置信区间(CI)、预测区间以及偏倚评估结果。

Output Format

输出格式

markdown
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markdown
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Meta-Analysis: [Research Question]

元分析:[研究问题]

Study Inclusion

研究纳入情况

CriterionValue
Studies included (k)xx
Total sample size (N)xxxx
Effect size metric[d / r / OR]
标准数值
纳入研究数量(k)xx
总样本量(N)xxxx
效应量指标[d / r / OR]

Pooled Effect Size

合并效应量

ModelEffect95% CIzp-value
Fixed-effectx.xx[x.xx, x.xx]x.xxx.xx
Random-effectsx.xx[x.xx, x.xx]x.xxx.xx
模型效应值95% CIzp值
Fixed-effectx.xx[x.xx, x.xx]x.xxx.xx
Random-effectsx.xx[x.xx, x.xx]x.xxx.xx

Heterogeneity

异质性分析

StatisticValueInterpretation
Qx.xx (p = x.xx)[significant/not]
x.xx%[low/moderate/high]
τ²x.xx[between-study variance]
统计量数值解释
Qx.xx (p = x.xx)[显著/不显著]
x.xx%[低/中/高]
τ²x.xx[研究间方差]

Publication Bias

发表偏倚检验

TestResultInterpretation
Funnel plot[symmetric/asymmetric][bias suspected?]
Egger's testp = x.xx[significant?]
Trim-and-filladjusted effect = x.xx[studies imputed: x]
检验方法结果解释
漏斗图[对称/不对称][是否怀疑存在偏倚?]
Egger检验p = x.xx[是否显著?]
剪补法调整后效应值 = x.xx[填补研究数量: x]

Limitations

局限性

  • [Note any assumption violations]
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  • [注明任何违反假设的情况]
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Gotchas

注意事项

  • Combining apples and oranges: statistically possible but conceptually meaningless if constructs differ
  • Random-effects models give more weight to small studies, which are often lower quality
  • I² depends on precision of included studies; low I² with imprecise studies does not mean homogeneity
  • Funnel plot asymmetry can be caused by factors other than publication bias (small-study effects)
  • File-drawer problem: unpublished null results are systematically missing
  • Moderator analyses with many subgroups and few studies per subgroup are underpowered and unreliable
  • 不当整合:若研究概念不同,即使统计上可行,概念层面也毫无意义
  • Random-effects模型会赋予小样本研究更高权重,而这类研究通常质量较低
  • I²的大小取决于纳入研究的精确性;若研究本身精度低,I²值小并不代表同质性
  • 漏斗图不对称可能由发表偏倚以外的因素导致(小样本效应)
  • 文件抽屉问题:未发表的无效结果被系统性遗漏
  • 若调节变量分析包含多个亚组且每个亚组的研究数量较少,统计效力不足,结果不可靠

References

参考文献

  • Borenstein, M., Hedges, L. V., Higgins, J. P. T., & Rothstein, H. R. (2009). Introduction to Meta-Analysis. Wiley.
  • Higgins, J. P. T., & Thompson, S. G. (2002). Quantifying heterogeneity in a meta-analysis. Statistics in Medicine, 21(11), 1539-1558.
  • Rothstein, H. R., Sutton, A. J., & Borenstein, M. (2005). Publication Bias in Meta-Analysis. Wiley.
  • Borenstein, M., Hedges, L. V., Higgins, J. P. T., & Rothstein, H. R. (2009). Introduction to Meta-Analysis. Wiley.
  • Higgins, J. P. T., & Thompson, S. G. (2002). Quantifying heterogeneity in a meta-analysis. Statistics in Medicine, 21(11), 1539-1558.
  • Rothstein, H. R., Sutton, A. J., & Borenstein, M. (2005). Publication Bias in Meta-Analysis. Wiley.