Data for: Statistical approaches in intra-subject designs. Using Single-Case Data Analysis in an early language intervention study with a multilingual late talker.

Observational Study - In order to evaluate the treatment effect of a language intervention for children with a history in late talking longitudinally, the present Single Case Experimental Design (SCED) consists of three phases (baseline (A), intervention (B), and follow-up (C)) with a total of 20 measurement time points. The data was collected between 2023 and 2024. For evaluating the risk for Developmental Language Disorder in the participant (pseudonym: Kian), parental questionnaires, nonword-repetition and vocabulary size in Polish, German and Bulgarian were assessed parallel to the baseline-phase. Standardized tests of expressive and receptive vocabulary in German were conducted at the beginning of the baseline- and at the end of the follow-up-phase. The longitudinal target variables regarding multimodal spontaneous speech were collected using video analysis (transcribing and coding) for each time point during the therapy sessions. Data analyses include pre-analyses (descriptive and visual), trend analyses and overlap statistics, and piecewise-regression models, as recommended by Masterson et al. (2018) and Wilbert (2024). Interrater reliability was analyzed for the video coding.