The Test of Gross Motor Development-Third Edition: A Bifactor Model, Dimensionality, and Measurement Invariance

Abstract

Aim: To examine the latent structure of the Test of Gross Motor Development, 3rd Edition (TGMD-3) with a bifactor modeling approach. Furthermore, the study examines the dimensionality, model-based reliability of general and specific contributions of the test's subscales and measurement invariance of the TGMD-3. Methods: Using a sample of 496 Iranian children (M age = 7.23±2.03 years; 53.8 female) from the five main geographic regions of Tehran city, three alternative measurement models were tested: (a) a unidimensional model, (b) a correlated 2-factor model, (c) a bifactor model. Results: The totality of results including item loadings, goodness-of-fit indexes and reliability estimates all supported the bifactor model and strong evidence of general fundamental movement factor. Additionally, the reliability of subscale scores was poor, it is thus contended that scoring, reporting and interpreting of the subscales scores are probably not justifiable. Suggesting that the 2 traditionally hypothesized factors are better understood as “grouping” factors rather than as representative of latent constructs. Furthermore, the bifactor model appears invariant for gender. Conclusion: This study is the first to address the bifactor model and new insights regarding the application and interpretation of the test battery most widely used with children.