Evaluating construct validity of the Slosson Visual-Motor Performance Test using the Rasch Measurement Model.

The aim of this study was to evaluate the construct validity of the Slosson Visual-Motor Performance Test by applying the Rasch Measurement Model to evaluate the test's scalability, dimensionality, differential item functioning based on sex, and hierarchical ordering. Participants were 400 children ages 5 to 12 years, recruited from six schools in Melbourne, Victoria, Australia. The Slosson Visual-Motor Performance Test requires a child to copy 14 different geometric designs three times each for a total 42 scale items. Children completed the test under the supervision of an occupational therapist. Overall, 13 of 42 of the test items exhibited poor measurement properties. As nearly one-third of the scale items were problematic, the Slosson Visual-Motor Performance Test in its current form is not recommended for clinical use.