* 被合并的簇的方差增量([[Ward标准]])<ref name="wards method">{{cite journal|doi=10.2307/2282967|last=Ward |first=Joe H. |title=Hierarchical Grouping to Optimize an Objective Function |journal=Journal of the American Statistical Association |volume=58 |issue=301 |year=1963 |pages=236–244}}</ref>.
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* 被合并的簇的方差增量([[Ward标准]])<ref name="wards method">{{cite journal|doi=10.2307/2282967|last=Ward |first=Joe H. |title=Hierarchical Grouping to Optimize an Objective Function |journal=Journal of the American Statistical Association |volume=58 |issue=301 |year=1963 |pages=236–244}}</ref>.