Background: We investigated how quiz activities can improve summative assessment outcomes by analyzing the relationship between them.Methods: We used 217 first-year medical students’ medical informatics data from 3 consecutive years. We analyzed summative assessment outcomes between quiz completion and incompletion groups, one-time and multiple-time quiz learning groups, and three combined comparisons between subgroups of quiz learning activity frequencies: 1 versus 2, 3, 4, and 6 (group 1), 1 and 2 versus 3, 4, and 6 (group 2), and 1, 2, and 3 versus 4 and 6 (group 3). We then analyzed correlations between the final quiz scores and summative assessment outcomes.Results: The summative assessment means for students who completed quizzes and those who did not were 87.16±8.73 and 83.22±8.31, respectively (p=0.001). The means for the one-time and multiple-time quiz learning groups were 86.54±8.94 and 88.71±8.10, respectively (p=0.223). The means for combined subgroups were not significantly different between groups (p>0.05), although a statistically significant increasing trend was found from groups 1 to 3 (0.223>0.203>0.075 using the t-test and 0.225>0.150>0.067 using the Mann-Whitney test, respectively). Summative assessment scores were not significantly correlated with quiz scores (r=0.115, p=0.213).Conclusions: Quizzes helped students who used self-directed learning obtain better summative assessment outcomes. Formative quizzes presumably did not provide students with direct knowledge, but showed them their weak points and motivated them to work on areas where their knowledge was insufficient.