This study aims to establish the relationship between university students’ motivation and how much they actually practice when learning English vocabulary using apps downloaded onto their mobile devices. The focus group, comprising 30 freshman students at Yuan Ze University, participated in this empirical study during the first semester of the 2015 academic year. The data collected from the questionnaires were analyzed by fuzzy nonparametric tests, including the Wilcoxon Sign Rank Test, the Wilcoxon Rank-Sum Test and the Kruskal-Wallis Test. The findings show how the focus group learned English vocabulary using the apps downloaded onto their smart phones. First, the participants were willing to use smart phone apps for academic purposes. Secondly, the variables of gender and faculty registration did not influence how much time was spent on these two games, indicating that mobile game-based learning can be implemented as a learning strategy for most university students. Finally, it was shown that the more time students spent playing English vocabulary games, the better their progress was compared with students who spent less time playing the games.