In practice quantitative performance measures have limited use while Usually qualitative measures are used.
Cluster are best validated using downstream tasks. The stability of the clusters is sometimes used to validate the clusters
Quantitative Metrics
- Single linkage: Smallest minimum distance
- Average linkage: Smallest average distance between all pairs in the clusters
- Complete linkage: Smallest maximum distance
- Ward: Smallest increase in within-cluster variance which leads to more equally sized clusters.