I recently got into a debate on how to best measure when my Facebook/Twitter/Instagram friends are most active. Imagine that I have the input data set that consists of (timestamp, user_id), where timestamp is the time when the user did something like posting a new status. Given this information, how would you measure when the most users would see your post? We can assume that we are going to quantize this to an hour or half hour interval.
My friend suggests that simply averaging the number of unique users engaged in any given hour isn't enough because not all users are active every day, but randomly during any given time of day, making all hours look the same in the long run. Thoughts?