Measurement invariance of TGMD-3 in children with and without mental and behavioural disorders

This study evaluated whether the Test of Gross Motor Development 3 (TGMD-3) is a reliable tool to compare children with and without mental and behavioural disorders across gross motor skill domains. A total of 1075 children (aged 3-11 years), 98 with mental and behavioural disorders and 977 without (typically developing), were included in the analyses. The TGMD-3 evaluates fundamental gross motor skills of children across two domains: locomotor skills and ball skills. Two independent testers simultaneously observed children’s performances (agreement over 95%). Each child completed one practice and then two formal trials. Scores were recorded only during the two formal trials. Multigroup Confirmatory Factor Analysis tested the assumption of TGMD-3 measurement invariance across disability groups. According to the magnitude of changes in Root Mean Square Error of Approximation and Comparative Fit Index between nested models, the assumption of measurement invariance across groups was valid. Loadings of the manifest indicators on locomotor and ball skills were significant (p < .001) in both groups. Item Response Theory analysis showed good reliability results across locomotor and the ball skills full latent traits. The present study confirmed the factorial structure of TGMD-3 and demonstrated its feasibility across normally developing children and children with mental and behavioural disorders. These findings provide new opportunities for understanding the effect of specific intervention strategies on this population.