Psychometric Properties of the Satisfaction With Life Scale in People With Traumatic Brain, Spinal Cord, or Burn Injury: A National Institute on Disability, Independent Living, and Rehabilitation Research Model System Study.

This study evaluated the measurement properties of the Satisfaction With Life Scale (SWLS) in a sample of 17,897 people with spinal cord injury (48%, n = 8,566), traumatic brain injury (44%, n = 7,941), and burn injury (8%, n = 1,390), 1 year following injury. We examined measurement invariance across the groups, unidimensionality, local independence, reliability from a classical test and item response theory (IRT) framework, and fit to a unidimensional IRT model. The results support unidimensionality and local independence of the SWLS. Reliability was adequate from a classical test and IRT perspective. IRT analysis found that the SWLS could be improved by using only five response categories rather than seven and by removing the fifth item, "If I could live my life over, I would change almost nothing." This item functions poorly and reduces instrument reliability. With these revisions, the SWLS is a useful instrument to monitor an important outcome of trauma rehabilitation.