
The game of Go involves a ranking system to allow people at different levels of strength to play fair games. The system is widely employed in both in-person and online games, and some variation of it is used by every major Go server and organization.
The ranks go from 30k to 1k, and then 1d to 9d. 1d is 1 rank (or "stone") from 1k, and 5k is 4 stones from 9k. There are some problems with this system (e.g., in reality the ratings are neither linear nor transitive), but they provide a good way of estimating someone's strength before you play them for the first time.
In this essay we are going to examine the KGS rating data from 16 March 2008 for confident ranks. One of the key skills in data analysis is an understanding that data is data, and so it is a useful exercise to examine arbitrary data sets to see what you can discover. With this in mind, let's examine the data and see what falls out.