Detecting individual change in children with mild to moderate motor impairment: the standard error of measurement of the movement

Objective: To assess whether the Movement ABC can be used to monitor individual change in motor performance. Design: Motor-impaired children were tested three times in succession with the Movement ABC without any intervention. Setting: Two schools for special education and one school for children who are chronically ill. Subjects: Three girls and 20 boys aged 6-8 years. Main outcome measures: Scores were measured per item (0→5), added to cluster scores (0→10 or 15), added to form the total scores (0→40). Mean scores, standard errors of measurement (SEMs) and least detectable differences (LDDs) were calculated per item, per cluster and for the total scores. A repeated measures analysis of variance was performed to test for the effects of time. Results: The total scores improved significantly from the first session (mean: 15.4 points) to the second (mean: 13.3), but not from the second to the third (mean: 13.2). Average item scores ranged from 0.6 to 2.7 points with SEMs of 0.79→1.54 and LDDs of 2.20→4.27. Average cluster scores ranged from 3.4 to 5.3 with SEMs of 1.51→1.84 and LDDs of 4.18→5.11. The SEM of the total scores equalled 3.13 with an LDD of 8.68. Conclusions: The total score of the Movement ABC is sufficiently sensitive to monitor individual change; the cluster scores have moderate sensitivity and individual items are inappropriate to monitor individual change. The significant effect of time is interpreted as an effect of learning.