Continuous vs categorical variable

[jgrant8]

Hello,

I am designing a DCE using Ngene which includes a continuous attribute with 3 levels (10, 15, 20). If the Ngene design specifies this attribute as continuous, is it essential that it is analysed as continuous in the logit model, or can it also be analysed as a categorical variable if this looks like a better fit at this stage? I read somewhere that you can design it as a non-linear/categorical and then analyse it as continuous but not vice-versa, but I am not sure why this would be the case.

Thanks very much for any help.