I am a new in using the Stata software and dealing with a mode choice experiment having three different alternatives of transport modes with three different attributes of cost, frequency, and time in order to select the most suitable mode based on the given variables. I use the following function in the command:

asclogit Chosen Cost Freq Time, case(Observation) alternatives(Alternative)

and I get a note that is saying: variable Freq has 152 cases that are not alternative-specific: there is no within-case variability

It will be highly appreciated if can someone helps with this issue.

Hamad