D-efficient design dominant alternatives?

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D-efficient design dominant alternatives?

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?
andreb84

Posts: 6
Joined: Tue Dec 03, 2019 10:25 pm

Re: D-efficient design dominant alternatives?

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
Michiel Bliemer

Posts: 1088
Joined: Tue Mar 31, 2009 4:13 pm

Re: D-efficient design dominant alternatives?

Thank you very much Michiel!
andreb84

Posts: 6
Joined: Tue Dec 03, 2019 10:25 pm