DS同学们一般怎么准备case题？顺便问一道case题

楼主看到了一道这样的case题：How would you test whether having more friends now increases the probability that aFacebook member is still an active user after 6 months?

目前我想到的是可以用historical data来看#friends和active engagement after 6 months的关系，从而来预测现在的

但觉得思路太单一了，请问还有什么角度吗？

顺便问问面ds的各位都是怎么准备case题的