Retest reliability is a better predictor of validity than is internal consistency. One explanation for this is item-specific variance, which distinguishes different nuances of a facet and contributes to retest reliability but not internal consistency. Specific variance at the facet level is temporally stable, consensually validated, and heritable; a consideration of the role of specific variance in personality measures leads to a distinction between traits as the intersection (∩) versus the union (∪) of their constituents. I discuss specific variance at the item level and its implications for scale development and argue that retest reliability outpredicts internal consistency because item-specific variance has been shown to be observable, and is probably heritable and stable. I consider some implications of these ideas for the use of single-item scales, the causal interpretation of traits, and the notion of scalar equivalence. Finally, I note that the sources of random error in scales are still poorly understood.

中文翻译：

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可靠性的细微差别在于：特质层次结构中的特异性。

与内部一致性相比，重新测试的可靠性更好地预测了有效性。对此的一种解释是特定于项目的差异，该差异区分了构面的不同细微差别，并有助于重新测试可靠性，但不能有助于内部一致性。构面级别上的特定方差在时间上是稳定的，经知情确认且可遗传。对人格测度中特定方差的作用的考虑导致了特质之间的区别，即特质的交集（∩）与并集（∪）。我讨论了项目级别的特定差异及其对规模发展的影响，并认为重新测试的可靠性高于内部一致性，因为已证明特定项目的差异是可观察的，并且可能是可遗传且稳定的。我认为这些想法对单项量表的使用，特质的因果解释以及标量等价概念有一些含义。最后，我注意到对刻度的随机误差的来源仍然知之甚少。