Differential item functioning (DIF) or measurement invariance (MI) testing for single-item assessments has previously been impossible. Part of the issue is that there are no conditioning variables to serve as a proxy for the latent variable--regression-based DIF methods. Another reason is that factor-analytic approaches require multiple items to estimate parameters. In this technical working paper, I propose an approach for evaluating DIF/MI in a single-item assessment of a construct. The current methods should NOT replace using multiple-indicator MG-CFA/IRT analyses of DIF/MI or regression mased methods when possible. More items generally provide significantly better construct coverage and provide more rigorous DIF/MI evaluation.

翻译：对于单项目评估的差异项目功能（DIF）或测量不变性（MI）检验，以往一直无法实现。部分问题在于缺乏可作为潜变量代理的条件变量——这是基于回归的DIF方法所必需的。另一原因是因素分析方法需要多个项目来估计参数。在本技术工作论文中，我提出了一种在构念的单项目评估中检验DIF/MI的方法。当前方法不应替代在可能情况下使用多指标多组验证性因素分析（MG-CFA）/项目反应理论（IRT）的DIF/MI分析或基于回归的方法。通常，更多项目能显著提升构念覆盖度，并提供更严格的DIF/MI评估。