This document discusses using statistical analysis of purchase history data to predict users' purchase intervals and remind them when it is time to purchase an item again. It finds that for the rice category, 47% of users have relatively fixed purchase intervals with only a few outliers. By detecting these fixed intervals, a reminder system could notify users just before their next predicted purchase to prevent them from forgetting to buy an item. This has the potential to benefit users while also promoting repeated purchases in various product categories.