Unbalanced attribute levels
Posted: Fri Aug 23, 2024 8:38 am
Good morning,
I am developing design for a choice experiment about preferences for trees on grazing lands. There are two discrete attributes, A and B, and two continuous attributes, C and D. A has 4 levels 0 (no trees) and 1, 2, 3 are different configurations. B are species: 1 native, 2 exotics, and 0 none. C is the extent: 0%, 10%, 30%. D is cost equivalent: 1, 2, 3. For attribute A = 0, attributes B and C are 0. For attribute A =[1, 2, 3], B and C <> 0. I would like 2 unlabelled alternatives. When I try to formulate the design, NGENE cannot find valid design.
What could be the approach for designing this choice experiment?
One approach I can think of is to use a labelled design with alt1 A=0 and alt2 A <> 0. But I would also like to explore tradeoffs between other combinations (where A <> 0) directly.
I am developing design for a choice experiment about preferences for trees on grazing lands. There are two discrete attributes, A and B, and two continuous attributes, C and D. A has 4 levels 0 (no trees) and 1, 2, 3 are different configurations. B are species: 1 native, 2 exotics, and 0 none. C is the extent: 0%, 10%, 30%. D is cost equivalent: 1, 2, 3. For attribute A = 0, attributes B and C are 0. For attribute A =[1, 2, 3], B and C <> 0. I would like 2 unlabelled alternatives. When I try to formulate the design, NGENE cannot find valid design.
- Code: Select all
Design
;alts = altA*, altB
;rows = 32
;block = 8
;eff=(mnl,d)
;cond:
if(alta.A = 0, alta.B = 0),
if(alta.A = 0, alta.C = 0),
if(altb.A = 0, altb.B = 0),
if(altb.A = 0, altb.C = 0),
if(alta.A <> 0, alta.B <> 0),
if(alta.A <> 0, alta.C <> 0),
if(altb.A <> 0, altb.B <> 0),
if(altb.A <> 0, altb.C <> 0)
;model:
U(altA) =
b1.dummy[0.2|0.3|0.4] * A[0, 1, 2, 3] +
b2.dummy[0.1|0.2] * B[0, 1, 2] +
b3[0.1] * C[0, 10, 30] +
b4[-0.1] * D[60, 90, 120] /
U(altB) = b1 * A + b2 * B + b3 * C + b4 * D
$
What could be the approach for designing this choice experiment?
One approach I can think of is to use a labelled design with alt1 A=0 and alt2 A <> 0. But I would also like to explore tradeoffs between other combinations (where A <> 0) directly.