1) Total SSE is the sum of the SSE for each separate attribute. (25) a. What does it mean if the SSE for one variable is low for all clusters? b. Low for just one cluster? c. High for all clusters? d. High for just one cluster? e. How could you use the per variable SSE information to improve your clustering?

2) Consider the mean of a cluster of objects from a binary transaction data set. a. What are the minimum and maximum values of the components of the mean? b. What is the interpretation of components of the cluster mean? c. Which components most accurately characterize the objects in the cluster?

3) Give an example of a data set consisting of three natural clusters, for which (almost always) K-means would likely find the correct clusters, but bisecting K-means would not.