Beyond translation: a multi-evidential validity argument for the school-adapted Arabic KTK

Background Performance-based motor assessments are frequently transferred across cultural and educational contexts under the assumption that translation alone preserves score meaning. However, school-based adaptations may alter the score-generating process and, consequently, the interpretations that can be supported. Using the Körperkoordinationstest für Kinder (KTK) as an empirical case, this study examined how a school-adapted Arabic version should be interpreted within a validity-argument framework. Methods A multi-evidential psychometric evaluation was conducted with 316 Saudi primary-school boys from eight schools. Evidence based on internal structure was examined using EFA, CFA, and split-sample replication, alongside reliability and measurement precision ( ω , ICC, SEM, MDC₉₅), measurement invariance, grade-related differentiation, practice effects, and preliminary external associations. Results Results supported a replicable one-factor coordination structure (CFI = 0.979), satisfactory composite reliability ( ω = 0.796), and good temporal stability (ICC = 0.870). The battery showed strong differentiation across grade levels ( η 2 = 0.419). Metric invariance was supported, whereas full scalar invariance was not, indicating that structural replication did not automatically justify unrestricted score comparisons. Systematic practice effects were observed for several subtests and the composite score, limiting straightforward interpretation of repeated measurements. The composite MDC₉₅ was 0.80 composite-score units. Because age and anthropometric data were not recorded, grade differences indicate cross-sectional grade-group differentiation rather than developmental change. Conclusion The findings extend beyond linguistic adaptation of the KTK by showing that performance-based assessments should be evaluated in terms of the score interpretations they support within a specific context. The School-Adapted Arabic KTK supports a coherent coordination construct and bounded use of the composite score, but does not justify direct application of the original German Motor Quotient classifications. More broadly, the study shows how evidence based on internal structure, reliability, measurement error, and measurement invariance can be considered together when defining defensible score use across cultural contexts. This shifts the focus of cross-cultural adaptation from translation alone to the validity of the inferences drawn from adapted scores.