Digit Span Subscale Scores May Be Insufficiently Reliable for Clinical Interpretation: Distinguishing Between Stratified Coefficient Alpha and Omega Hierarchical

The Digit Span subscale (Digit Span Forward, Backward, and Sequencing combined composite) internal inconsistency reliability has been reported at .93, based on a coefficient known as stratified coefficient alpha. With accessible examples, we demonstrate that stratified coefficient alpha can deviate substantially from a model-based internal consistency reliability that represents an underlying dimension, that is, omega hierarchical. Next, we...