SPSS Statistics offers three clustering procedures: CLUSTER, QUICK CLUSTER, and TWOSTEP CLUSTER.
CLUSTER produces hierarchical clusters of items based on distance measures of dissimilarity or similarity. The items being clustered are usually rows in the active dataset, and the distance measures are computed from the row values for the input variables. Hierarchical clustering produces a set of cluster solutions from a starting situation where each case is its own cluster of size one, to an ending situation where all cases are in one cluster. Case-to-case distance is unambiguous, but case-to-cluster and cluster-to-cluster distance can be defined in different ways, so there are multiple methods for agglomeration, which is the bring together of objects or clusters.
This form of clustering is called hierarchical because cluster...