Which statistic indicates the internal reliability of multiple-item self-report scales?

The statistic that indicates the internal reliability of multiple-item self-report scales is Cronbach's alpha. This coefficient assesses the extent to which all items on a test measure the same underlying construct. A high Cronbach's alpha value (typically above 0.70) suggests that the items are highly correlated and thus reliably measure the same concept, making it a critical tool in psychological research and scale development.

On the other hand, while the alpha coefficient mentioned in the choices refers to the same concept, the term most commonly used and recognized in research contexts is Cronbach's alpha. Standard deviation measures the amount of variation or dispersion of a set of values, and variance describes how much the values differ from the mean, but neither directly assesses reliability in the context of self-report scales. These other statistics do not provide insight into the internal consistency of the items within a scale, which is the central focus of assessing reliability in this scenario.