Effectiveness of GenAI in enhancing writing performance: a meta-analysis

Abstract This meta-analysis synthesized empirical evidence on the effects of generative artificial intelligence (GenAI)–supported writing instruction on students’ L2/EFL writing outcomes and examined key moderators. Effect sizes were calculated as Hedges’ g and synthesized using random-effects (DerSimonian–Laird) models. Robustness checks included cluster-robust variance estimation (RVE), sensitivity analyses, prediction intervals, and publication-bias diagnostics (Egger, Begg, PET-PEESE). The primary random-effects model yielded a statistically significant pooled effect (g = 0.80, 95% CI [0.37, 1.22]), indicating a large advantage for AI-enhanced writing instruction. Heterogeneity was substantial (I 2 = 92.21%). Publication-bias tests were non-significant. Robust meta-regression showed that risk-of-bias classification significantly moderated effects (β = 0.93, p = 0.014), whereas instructional model, duration, and sample size were non-significant. AI-enhanced writing instruction demonstrates a positive average effect, though effectiveness appears contingent upon methodological and contextual factors.