(TGMD-3) Test of Gross Motor Development, Third Edition

New Features in the Third Edition

•        All-new normative data were collected from 2014 to 2017.
•        Characteristics of the normative sample relative to socioeconomic factors, gender, disability, and other critical demographics are the same as those projected by the 2017 U.S. Census and are representative of the current U.S. population.
•        The normative information is stratified by age relative to geography, gender, race, ethnicity, household income, and parent education level.
•        Items were added to each subtest to eliminate possible ceiling effects.
•        New and extensive studies of test bias (both differential item functioning and subgroup comparison studies) were conducted, indicating that the TGMD-3 possesses little or no bias regarding gender, race, or ethnicity.
•        New and extensive studies of the floors, ceilings, and item gradients for the TGMD-3’s subtests and composite were conducted. The results indicate that the TGMD-3 has substantial and consistently good-to-excellent floors and ceilings.
•        All-new reliability and validity studies were prepared, including diagnostic accuracy analyses, which are considered the most rigorous techniques for establishing validity today. These analyses involve the computation of sensitivity and specificity indexes and the receiver operating characteristic/area under curve (ROC/AUC) statistic.
•        Additional studies of construct-identification validity, including studies of age differences, subgroup performance, exploratory factor analysis, and confirmatory factor analysis of the test’s structure, were provided. The results of these studies indicate that the TGMD-3’s internal structure is sound and its results are valid.

Subtests and Scores

The TGMD-3 has two subtests. The first subtest, Locomotor, measures the gross motor skills that require fluid, coordinated movements of the body as the child moves in one direction or another. The second subtest, Ball Skills, measures the gross motor skills that demonstrate efficient throwing, striking, and catching movements. 

The TGMD-3 provides an overall composite (Gross Motor). The two subtest scaled scores are combined to form the Gross Motor composite. The Examiner’s Manual discusses the test’s theoretical and research-based foundation, item development, standardization, administration and scoring procedures, normative tables, and guidelines for using and interpreting the test’s results.

The average coefficient alpha is .88 for the Locomotor subtest and .89 for the Ball Skills subtest, and is .93 for the composite. New validity studies demonstrate the test’s ability to differentiate children with cognitive impairments and autism spectrum disorder from typically developing children. For the cognitive impairment sample, a Gross Motor Index cutoff score of 90 resulted in a sensitivity of .71, a specificity of .91, and a ROC/AUC of .87. For the autism spectrum disorder sample, a Gross Motor Index cutoff score of 85 resulted in a sensitivity of .76, a specificity of .91, and a ROC/AUC of .86.