A deep understanding of the learning level of online learners is a critical factor in promoting the success of online learning. Using knowledge structures as a way to understand learning can help analyze online students’ learning levels. The study used concept maps and clustering analysis to investigate online learners’ knowledge structures in a flipped classroom’s online learning environment. Concept maps (n = 359) constructed by 36 students during one semester (11 weeks) through the online learning platform were collected as analysis objec...