Pick the Mistake Before You Pick the Metric
TL;DR for operators A clustering score is not a neutral verdict. It is a policy for deciding which mistakes count. Pasi Fränti’s review of external clustering measures separates that policy into three choices: how predicted clusters are matched to reference clusters, how similarity is scored, and how results are normalized.1 Those choices determine whether the metric rewards getting many individual records right, getting each cluster right regardless of size, or locating the correct cluster structure. ...