  The paper presents a cursory examination of clustering, focusing on a rarely
explored field of hierarchy of clusters. Based on this, a short discussion of
clustering quality measures is presented and the F-score measure is examined
more deeply. As there are no attempts to assess the quality for hierarchies of
clusters, three variants of the F-Score based index are presented: classic,
hierarchical and partial order. The partial order index is the authors'
approach to the subject. Conducted experiments show the properties of the
considered measures. In conclusions, the strong and weak sides of each variant
are presented.
