Solving a Data Science Problem

Vincent Granville on ways to solve a data science problem. An interesting case study that uses a number of common analytic methods.  Well described:  " .... Here we discuss four approaches to solve the following marketing problem: identify, each day, the most popular Google groups, within a large list of target groups. You want to post in these groups only. The only information that is quickly available for each group, is the time when the last posting occured. Intuitively, the newer the last posting, the most active the group. There are some caveats such as groups where all postings come from one single user - a robot - for instance groups that focus on posting job ads exclusively. They should be in your black list.... "