The present study involved the analysis of 81 second language instructed vocabulary acquisition (L2 IVA) studies over 2 phases. In Phase I, we categorized and coded the effect sizes of the studies. Observing that the basic between‐ and within‐subject design dichotomy lacked the sensitivity to capture the heterogeneity of observed effects, we employed a more granular approach. In both between‐ and within‐subject designs, treatment versus comparison contrasts best represented comparisons of most interest in L2 IVA experiments, with median effect sizes (g) of .62 (between‐subject) and .25 (counterbalanced within‐subject). In Phase II, the aggregated effect sizes observed in Phase I were utilized in a priori power simulations to suggest approximate sample sizes for common L2 IVA analyses. For conservatively powered between‐subject designs, the simulations suggested sample sizes ranging from 292 to 492 participants. Counterbalanced within‐subject designs required 95 to 203 subjects depending on the assumed correlation between the repeated measures. The overarching implication of these simulations suggests that future L2 IVA experiments require larger samples that reference effect sizes from previous research, and we offer 3 potential solutions to the problem of obtaining larger samples.

中文翻译：

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第二语言指导的词汇习得研究中的效果驱动样本量

本研究涉及两个阶段的81种第二语言指示性词汇习得（L2 IVA）研究的分析。在第一阶段，我们对研究的效果大小进行了分类和编码。观察到受试者之间和受试者内部的基本二分法缺乏捕获观察到的效应异质性的敏感性，因此我们采用了更细化的方法。在受试者之间和受试者内部的设计中，治疗与比较对比最能代表L2 IVA实验中最感兴趣的比较，且中位效应大小（g）（0.62）（介于主题之间）和.25（平衡于主题内部）。在阶段II中，在先验功率模拟中利用了在阶段I中观察到的合计效应大小，以建议常见L2 IVA分析的近似样本大小。对于保守的受试者间设计，模拟建议的样本量范围为292至492名参与者。平衡的主题内设计需要95至203个主题，具体取决于重复测量之间的假定相关性。这些模拟的总体含义表明，未来的L2 IVA实验需要更大的样本，这些样本应参考先前研究的效应大小，并且我们针对获得更大样本的问题提供了3种潜在解决方案。