Scores of typically developing children on the Peabody Developmental Motor Scales: infancy to preschool.

Norms for the Peabody Developmental Motor Scales (PDMS) and the Peabody Developmental Motor Scales, second edition (PDMS-2) are based on cross-sectional data that do not provide information on how the scores of individual children vary over time. This study examined intra-individual variability of PDMS fine and gross motor scores of 77 typically developing children at 9, 11, 13, 16, and 21 months of age and PDMS and PDMS-2 fine and gross motor scores at 4 years. Correlations between scores over time ranged from .13 to .45. PDMS and PDMS-2 scores were correlated at .71 and .75 with significantly different means, indicating that the two versions are not equivalent for 4-year-old children. Most children scored above the 16th percentile, the suggested cut-off on the PDMS, at both 21-month and 4-year assessments, but their percentile ranks fluctuated considerably. Use of confidence intervals contributes to accurate interpretation of scores by differentiating true change in a child's score from change due to measurement error.