D-efficient design dominant alternatives?

[andreb84]

Dear all,
I've generated the following efficient design. I don't know the priors but I know the sign so I put a small number as priors:

Code: Select all

Design
;alts=SQ, alt2, alt3
;rows=10
;eff=(mnl,d)
;model:
U(SQ) = b1[-0.0001] * TAX[109] + b2[0.0001] * PROD[60] + b3[0.0001] * PER[100] + b4[0.0001] * CHIL[100]/
U(alt2) = b1 * TAX1[25,50,109,200,300] + b2 * PROD1[30,60,90,120] + b3 * PERF1[50,100,150,200] + b4 * CHIL1[50,100,200,300] /
U(alt3) = b1 * TAX1 + b2 * PROD1 + b3 * PERF1 + b4 * CHIL1
$

However, In some choice task I have some clearly dominant alternative, for example in one case the two alternatives have a greater level of TAX (which has a negative prior) than the status quo and a lower level of all the other attributes (which have positive prior) than the status quo.
Is this possible? Is because the priors are very small number? What do you suggest?
Thank you for your attention

[Michiel Bliemer]

You need to tell Ngene which alternatives are generic/unlabelled such that it can check for dominance. You need to set the following:
;alts=SQ*, alt2*, alt3*

If the signs of your priors are set correctly, this will remove all dominant alternatives in your choice tasks.

Michiel

[andreb84]

Thank you very much Michiel!