Abstract
With the development of "flipped classroom" concept and increasing usage of web-based learning platforms in foreign language teaching field, the effectiveness of online instant feedback come into researchers' focus, and whether or not teachers should provide choices of feedback medium also becomes an issue. The following study assesses the effects of feedback medium as well as the effectiveness of offering students feedback medium choices. This in-progress large-scale randomized controlled trial is conducted using ASSISTments, an adaptive online tutoring platform.