Subskalen

Subskalen are subsidiary scales within a broader psychometric instrument, designed to measure specific domains or constructs contained in the overall assessment. They provide a more granular view than a single composite score and help distinguish patterns of strengths and weaknesses across areas such as function, mood, or behavior.

Construction and purpose: Subscales are formed by grouping items that share a common underlying construct, typically identified through factor analysis or guided by theory. Items within a subscale should be coherent and relatively independent from items in other subscales. Some instruments define subscales a priori, others derive them empirically to reflect distinct facets of the measured construct.

Scoring and interpretation: Subscale scores are usually computed by summing or averaging the responses of their items; some instruments use weighting if items contribute unequally. Scores are interpreted within the domain they represent, and higher scores typically indicate more of the characteristic measured, though this can vary by instrument. Handling missing data is a practical consideration in scoring subscales.

Reliability and validity: Subscales are evaluated for internal consistency (for example, Cronbach’s alpha), test-retest reliability, and various forms of validity, including construct validity and factor structure. Validity evidence often includes correlations with related measures and replication of the subscale’s factor structure.

Examples and considerations: In widely used surveys, the SF-36 contains several subscales (eg, physical functioning, pain, general health). Other instruments, such as the Multidimensional Fatigue Inventory or the Child Behavior Checklist, are organized into distinct subscales. Researchers should consider sample size for reliable estimation, potential multiple testing issues, and measurement invariance when comparing subscale scores across groups.