Two Step Cluster is IBM's brand name for a variant of Mixed-Mode Cluster Analysis.
The key differences between the two methods are that:
- Q's algorithm can also address MaxDiff, ranking, conjoint and discrete choice data (whereas these first need to be treated as numeric data in the IBM algorithm).
- Q assumes spherical clusters by default. This can changed by setting Distribution to Multivariate - Diagonal in the Advanced option.
Notes
Further reading: Latent Class Analysis Software.