I have plant biomass and grain weight data for different plant varieties which I now need to cluster. Do I need to define the number of clusters if using Ward's method and Squared Euclidean distance in SPSS? Also both of the variables are measured in same units so do I need to standardize this data?
Ward's method is a hierarchical clustering procedure, so number of cluster is not required to start (unlike k-means procedure, which requires number of cluster to be given beforehand).
Standardization is not required if the two dimensions are roughly on the same magnitude.