Evaluation of the Psychometric Properties of the Persian Version of the Test of Gross Motor Development–3rd Edition

The Test of Gross Motor Development–3rd Edition (TGMD-3) is an instrument for measuring gross motor development in children with and without a disability. This study aims to evaluate the psychometric properties of the Persian version of the TGMD-3 in 3- to 10-year-old Iranian children. The TGMD-3 was administered to 1,600 children (M age = 6.56 ± 2.29 years; 50% boys). The content validity of the TGMD-3 was established by five experts while its reliability was assessed through calculating internal consistency, test–retest, intra-rater, and inter-rater reliability coefficients. All reliability indices were excellent (>.82). The two-factor model was validated using confirmatory factor analysis. Adequate fit indices were found for the two-factor model (χ2 (64) = 389.02, p < .05, root mean square error of approximation (RMSEA) = .056, goodnesss of fit index (GFI) = .96, adjusted goodness of fit index (AGFI) = .94, normed fit index (NFI) = .96, non-normed fit index (NNFI) = .96, comparative fit index (CFI) = .96, incremental fit index (IFI) = .96, standardized root mean square residual (SRMR) = .03). An alternative one-factor model was also tested. Adequate fit indices in a one-factor model were found (χ2 (65) = 615.88, p = .0001, RMSEA = .07, GFI = .94, AGFI = .92, NFI = .98, NNFI = .98, CFI = .98, IFI = .98, SRMR = .03). The psychometric properties of the Persian version of TGMD-3 in Iranian children were supported and users can confidently use this test to evaluate gross motor development in Iranian children.