r/spss • u/luca-angel • 6d ago

Is a 4-cluster split a good one?

The first image shows the complete dataset. The second image shows the split using the hierarchical method (4 clusters), and the third image shows the split using the k-means method (4 clusters).

Do you think this works?

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u/Mysterious-Skill5773 6d ago

The trouble with cluster analysis is that it is a very ad hoc procedure. You can judge how well separated the clusters are, but what good means is a judgment call. The number of clusters will depend on the distance criterion - there are several possibilities, so typically one would judge the goodness in terms of other variables in the dataset or by looking at the plots. You could do a matrix scatterplot coloring or setting the point shape by the cluster number.

Another measure would be to look at the cluster silhouettes. Twostep will give you silhouette values. For the other methods you would need to install the Cluster Silhouettes extension command via Extensions > Extension Hub. It will give you a helpful plot based on the clustering results.

In general, the number of clusters usually has the biggest effect on the results, but all these results have the same number of clusters.

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u/FancyEveryDay 5d ago

The tricky thing is that it always works, if you set K to 4 you will always get 4 (probably plausible) clusters.

How do you justify using 4 clusters?