利用多元线性回归和条件分位数模型，测算了翻转教学对大学生外语习得的影响幅度及有效边界。研究发现：1）翻转教学能够显著提高二语习得效率；2）学习者阅读水平提升最大，而听力和写作水平提升较小且在高位出现了增长收敛，说明翻转教学能够促进学习者对语言基本知识的学习，但对深层次语言加工能力的影响有限；3）翻转教学存在区间效应，其高效性源于中低及以下水平学习者语言能力提升，中高及以上水平学习者从中获益较少。

We ran both the multivariate linear regression and conditional quantile regression on the data collected from a 17-week flipped College English intervention so as to measure and decompose its effect on students’ L2 acquisition. Results show that the flipped intervention significantly improves learners’ language performance. Specifically, the learning returns in the flipped context is through reading, listening and writing in the rank of weakening importance, with the growth convergence surfacing at the high end of the spectrum, which indicates that the flipped classroom helps to build up learners’ basic language knowledge but fails to improve their deep-level language processing capacity. We also find that the flipped intervention also causes interval effects as its efficiency stems from the improvement of the performance of students at middle- and lower- level while high achievers show limited improvements.