I've been given a segmentation in which people are segmented into, say, 6 groups on the basis of some number of survey questions. The segmentation is based on a cluster analysis of some sort.
My task is to use a different, second set of information to see how well that can recover the assignment to segments. (This is because this second set is available for many more respondents.) I can measure the accuracy on this part by a confusion matrix.
BUT, my ability to do this is limited by the reliability of the initial segmentation itself. The people who generated the segmentation think of it as gospel, and have provided no metrics.
What should I ask them to do? What's the best way to measure how reliable that initial segmentation is?