The result of a meta-analysis is conventionally pictured in the forest plot as a diamond, whose length is the 95% confidence interval (CI) for the summary measure of interest. The Diamond Ratio (DR) is the ratio of the length of the diamond given by a random effects meta-analysis to that given by a fixed effect meta-analysis. The DR is a simple visual indicator of the amount of change caused by moving from a fixed-effect to a random-effects meta-analysis. Increasing values of DR greater than 1.0 indicate increasing heterogeneity relative to the effect variances. We investigate the properties of the DR, and its relationship to four conventional but more complex measures of heterogeneity. We propose for the first time a CI on the DR, and show that it performs well in terms of coverage. We provide example code to calculate the DR and its CI, and to show these in a forest plot. We conclude that the DR is a useful indicator that can assist students and researchers to understand heterogeneity, and to appreciate its extent in particular cases.

中文翻译：

---

钻石比率：荟萃分析中异质性程度的视觉指标

Meta 分析的结果通常在森林图中被描绘为菱形，其长度是感兴趣的汇总度量的 95% 置信区间 (CI)。钻石比率(DR) 是随机效应荟萃分析给出的钻石长度与固定效应荟萃分析给出的钻石长度之比。DR 是一个简单的视觉指标，显示从固定效应到随机效应荟萃分析所引起的变化量。大于 1.0 的 DR 值增加表明相对于效应方差的异质性增加。我们研究了 DR 的特性，以及它与四种常规但更复杂的异质性测量的关系。我们首次在 DR 上提出 CI，并表明它在覆盖方面表现良好。我们提供示例代码来计算 DR 及其 CI，并在森林图中显示它们。我们得出结论，DR 是一个有用的指标，可以帮助学生和研究人员了解异质性，并在特定情况下了解其程度。