There has been an increased level of attention devoted to the consequences of test use in recent years; however, the majority of washback studies focused on teaching. In fact, little research has addressed learners' perspectives to analyze possible determinants of test results. To address this issue, this study first compared the pre-and-post standardized English tests of two groups of Taiwanese university students, and six students from each of the groups were interviewed at a later date to investigate the possible factors that may influence their score gains. A control group of 140 Taiwanese university students at a school without any English proficiency certificate exit requirement was compared to a contrast group of 136 similar students at a school that required the students to pass an English certification test in order to graduate. The major finding indicates that the amount of time spent on language learning plays an essential role in determining the degree to which student scores improve. This study subsequently offers pedagogical implications for the instruction of English at institutes of tertiary education.