In Study I, data for 1346 participants from Middle Europe and 144,143 participants from other world regions were analyzed. The participants were between the ages of 3 and 103 years, and they were well or had a variety of diagnoses. The results revealed that overall the item difficulty calibration values of the AMPS remained stable and that only one out of 36 ADL items of the AMPS demonstrated differential item functioning (DIF), but this DIF did not lead to differential test functioning (DTF).
In Study II, data for 11,189 typically-developing children from Middle Europe and other world regions who were between the ages of 2 and 15 were analyzed. The results of ANOVAs revealed significant effects for mean ADL motor and for ADL process ability measures by region and a significant age by region interaction effect for mean ADL process ability. Out of 168 estimated contrasts between Middle Europe and the other world regions for mean ADL motor and ADL process ability, only seven were statistically significant (4.17%), and only two were more than ±1 SE from the international means.
In Study III, regression analyses of data for 10,998 children, 4 to 15 years, who were typically-developing or with ADHD, DCD, LD, and SI, revealed significant age by group interaction effects. Post hoc t tests revealed significant group differences in ADL ability at all ages beyond the age of 4. ADL process ability effect sizes were moderate to large at all ages and ADL motor ability effect sizes were mostly moderate to large age 6 and above.
In Study IV, the use of the AMPS within the context of a feasibility study based on data for 17 Swiss children with ADHD, DCD, LD, and SI and 10 occupational therapists was evaluated. The analyses revealed several strengths and problems that were related to the time, equipment, and materials for administering the AMPS, the adherence to standardized administration procedures, the scope of the AMPS as a test of ADL performance, and the reliable rating by the blinded rater.