Baby Observational Selective Control AppRaisal (BabyOSCAR): Construct validity and test performance

AimTo investigate the construct validity of the Baby Observational Selective Control AppRaisal (BabyOSCAR), an assessment of independent joint motion in infants with cerebral palsy (CP).MethodBabyOSCAR was scored for 75 infants (45 with CP and 30 without CP). Rasch analysis was used in combination with classical test theory to assess areas of strength or improvement. Overall fit and precision, unidimensionality, local independence, reliability indices, Wright's child-item map, and differential item functioning were examined as part of Rasch analysis to investigate the item properties, internal construct validity, and reliability of BabyOSCAR. Cronbach's alpha was used to evaluate items' internal consistency.ResultsAnalysis demonstrated good fit to the Rasch model, with only one erratic item. Unidimensionality results suggest two dimensions, split between arm and leg items. Item calibration reliability was between 0.84 and 0.86, with three distinct item difficulty levels. Infant measure reliability was between 0.82 and 0.91, separating infants into three ability levels. Together, the two subscales covered the full range of skills, with redundancy mostly between the same motion on both sides of the body. Cronbach's alpha was between 0.90 and 0.95.InterpretationBabyOSCAR's construct validity was supported. Arm and leg subscales can be translated to a logit scale. The BabyOSCAR demonstrated excellent construct validity using Rasch analysis and classical test theory. Two subscales compliment one another well to comprise a total score. Items represent a continuum of skills with disctinct ability levels where some items are more likely to be seen in infants without cerebral palsy.image