The definition of single linkage says: In single linkage method, the distance between two clusters is defined as the minimum distance between two data points in each cluster.
However, different articles on clustering contradicts the above statement. The single linkage will create very loose clusters. Hence, the intra clusters variance would be high.
When the distance between two points is low then clusters would be tight cluster and variance should be low. Can someone throw some light to understand how loose clusters with high variance are formed with single linkage.