Effect size reporting is crucial for interpretation of applied research results and for conducting meta-analysis. However, clear guidelines for reporting effect size in multilevel models have not been provided. This report suggests and demonstrates appropriate effect size measures including the ICC for random effects and standardized regression coefficients or f2 for fixed effects. Following this, complexities associated with reporting R2 as an effect size measure are explored, as well as appropriate effect size measures for more complex models including the three-level model and the random slopes model. An example using TIMSS data is provided.

中文翻译：

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多级模型的效果量度：定义，解释和TIMSS示例

效应量报告对于应用研究结果的解释和进行荟萃分析至关重要。但是，尚未提供用于报告多层次模型中效应大小的明确指南。该报告提出并证明了适当的效应量度指标，包括随机效应的ICC和固定效应的标准化回归系数或f2。此后，探索了与将R2报告为效应大小度量相关的复杂性，以及适用于更复杂模型（包括三级模型和随机斜率模型）的适当效应大小度量。提供了使用TIMSS数据的示例。