Although the root‐mean squared deviation (RMSD) is a popular statistical measure for evaluating country‐specific item‐level misfit (i.e., differential item functioning [DIF]) in international large‐scale assessment, this paper shows that its sensitivity to detect misfit may depend strongly on the proficiency distribution of the considered countries. Specifically, items for which most respondents in a country have a very low (or high) probability of providing a correct answer will rarely be flagged by the RMSD as showing misfit, even if very strong DIF is present. With many international large‐scale assessment initiatives moving toward covering a more heterogeneous group of countries, this raises issues for the ability of the RMSD to detect item‐level misfit, especially in low‐performing countries that are not well‐aligned with the overall difficulty level of the test. This may put one at risk of incorrectly assuming measurement invariance to hold, and may also inflate estimated between‐country difference in proficiency. The degree to which the RMSD is able to detect DIF in low‐performing countries is studied using both an empirical example from PISA 2015 and a simulation study.

中文翻译：

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RMSD对表现欠佳的国家/地区的商品不匹配问题的敏感性

尽管均方根偏差（RMSD）是在国际大规模评估中用于评估特定国家/地区项目级别失配（即差异项目功能[DIF]）的一种流行的统计方法，但本文显示了其检测失配的敏感性。可能在很大程度上取决于所考虑国家的熟练程度分布。具体而言，即使存在非常强的DIF，RMSD也很少将一个国家/地区中大多数受访者提供正确答案的可能性很低（或很高）的项目标记为显示不合适。随着许多国际大规模评估计划逐渐覆盖范围更广的国家/地区，这引发了RMSD检测项目级失配，尤其是在表现不佳的国家/地区，这些国家与测试的总体难度水平不符。这可能会使一个人错误地假设测量不变性成立，也可能夸大估计的国家之间的熟练度差异。使用PISA 2015的经验示例和模拟研究，研究了RMSD在表现欠佳的国家/地区中检测DIF的程度。