Error Sum of Squares (SSE) is the sum of the squared differences between each observation and its group's mean. It can be used as a measure of variation within a cluster. If all cases within a cluster are identical the SSE would then be equal to 0. Anyone can give an example of calculating SEE? since it seems my results will be far away from 0, while I see the results on the previous work are quite close to 0. How this could be justified?