Measuring speech sound development: an item response model approach.

Research Aim: The primary aim of our study is to investigate if there is an ordering in the speech sound development of children aged 3-6, similar to the ordering in general language development.

Method: The speech sound development of 1035 children was tested with a revised version of Logo-Articulation Assessment. The data were analyzed with the Mokken Scale Program (MSP) in order to construct scales with satisfactory scalability (H-coefficient) and sufficient reliability (rho).