Comparing AI-enhanced instructional designs for EFL postgraduate proficiency: a multisite randomized controlled trial with exploratory ICC outcomes

No randomized evidence directly compares immersive simulation, intelligent pairing, and adaptive learning instructional designs within the same postgraduate EFL study using a standardized proficiency endpoint. This multisite randomized controlled trial compared three AI-enhanced instructional designs—structured task bundles delivered via AI mediation and evaluated as instructional designs rather than technology platforms—specifically Immersive Simulation Technology (IST), Intelligent Pairing Systems (IPS), and Adaptive Learning Platform (ALP)—with an active control in required postgraduate TESOL coursework at four East Asian university sites (N = 245) over 12 wk. The preregistered confirmatory outcome was official ETS-administered TOEFL iBT total score; Intercultural Communicative Competence Performance-Oriented (ICC-PO) performance was analyzed as a secondary exploratory outcome. Within the preregistered confirmatory proficiency family, all three Holm–Bonferroni-corrected contrasts were supported: IST outperformed Control and ALP, and ALP outperformed Control on TOEFL iBT total score; IPS proficiency contrasts were exploratory. IST produced the largest adjusted gain (Δ = 36.99 TOEFL points, 95% CI [35.58, 38.44]; Hedges’ g = 3.02, 95% CI [2.65, 3.39]; d_resid = 5.67), interpreted as a near-transfer, high-dose, context-specific upper-bound estimate rather than a population-average expectation. Exploratory ICC-PO patterns broadly paralleled the proficiency results but are interpreted cautiously as context-bound performance differences under a partially aligned instrument, with cross-group measurement comparability not established. The study contributes head-to-head randomized evidence for instructional-design selection—not technology novelty—and supports a sequenced pedagogical logic in which ALP, IPS, and IST serve distinct roles in postgraduate EFL instruction.