Retrieval performance was measured as follows: correct documents in the selected cluster total correct documents in the dataset where a correct document is one that contains all the words in a query, and the selected cluster is that whose centroid has the highest average value for the query terms.
if a query comprises the words , and cluster 7 has a centroid value © ¢ for word , then the cluster that best matches the query is the cluster Our measure for retrieval performance considers only recall (i.e.