I am a very new user of Ngene and choice experiment design generally. When you need one attribute completely dependent on another, should it be introduced as a constraint, or do you simply make a design with one fewer attributes?
Example code is below for a design with:
- 3 2-level variables (qualitative), 2 of which are completely dependent on each other
- 1 4-level quantitative variable
- an opt-out alternative (alt3):
- Code: Select all
Design
;alts = alt1, alt2, atl3
;rows=12
;block=4
;eff=(mnl,d)
;cond:
if(alt1.project=1, alt1.location=1),
if(alt1.project=2, alt1.location=2),
if(alt2.project=1, alt2.location=1),
if(alt2.project=2, alt2.location=2),
;model:
U(alt1)=cost[0]*cost[1,3,7,10]+project.dummy[0]*project[1,2]+location.dummy[0]*location[1,2]+type.dummy*type[1,2]
U(alt2)=cost[0]*cost[1,3,7,10]+project.dummy[0]*project[1,2]+location.dummy[0]*location[1,2]+type.dummy*type[1,2]
U(alt3)=asc
$
This code produces MNL D-errors of >1500 and I'm also not sure if that is a concern or not.