Description and Prediction of Slashdot Activity

We perform a statistical analysis of user's reaction time to a new discussion thread in online debates on the popular news site Slashdot. First, we show with Kolmogorov- Smirnov tests that a mixture of two log-normal distributions combined with the circadian rhythm of the community is able to explain with surprising accuracy the reaction time of comments within a discussion thread. Second, this characterization allows to predict intermediate and long-term user behavior with acceptable precision. The prediction method is based on activity-prototypes, which consist of a mixture of two log-normal distributions, and represent the average activity in a particular region of the circadian cycle.