'English Practice' is a mobile learning app that allows learners to test their English grammar usage. In this study, we observed 97,746 users and the results showed there are some factors might have certain influence on taking quiz score such as continent, country, time taking Quiz, and device screen size. First, learners who are from Europe tend to have the highest score. Asian learners ranked last in the list. Second, quiz answers in the morning and night had higher correct rate than in the afternoon and evening answers. Third, the screen size of mobile screen has possible correlation with Quiz score, as learner used a bigger screen, they got higher score. Moreover, research via store is one of the ways to conduct a research for mobile app and help us have more understanding about the users as well as get more clues to improve the apps, drive efficient marketing campaigns, and create a more pleasant experience for your users.