Reliability and Validity of the ACTIVE-mini for Quantifying Movement in Infants With Spinal Muscular Atrophy

The purpose of this study is to investigate the measurement properties of the Ability Captured Through Interactive Video Evaluation-mini (ACTIVE-mini) for quantifying movement in infants with Spinal Muscular Atrophy (SMA). Specifically, I will investigate within-day and between-day test-retest reliability and calculate the minimal detectable change of the ACTIVE-mini. Additionally, I will determine the concurrent validity of the ACTIVE-mini with The Children\'s Hospital of Philadelphia Infant Test for Neuromuscular Disease (CHOP INTEND) and the construct validity of the ACTIVE-mini in infants with SMA using a known group methodology.