We show that there is no formal statistical testing method to support combining categories in a standard ordered regression model. We discuss practical implications of this result.

doi.org/10.1111/j.1467-9574.2009.00432.x, hdl.handle.net/1765/18569
Econometric Institute Reprint Series
Statistica Neerlandica
Erasmus Research Institute of Management

Franses, P. H., & Cramer, M. (2010). On the number of categories in an ordered regression model. Statistica Neerlandica, 64(1), 125–128. doi:10.1111/j.1467-9574.2009.00432.x