Problem of OOD design

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Problem of OOD design

Postby wxy008 » Thu Apr 02, 2020 6:33 am

Hi Michiel,

Hope everything goes well for you.

I got 0% of D optimality when I run a ood design. the codes I run is below. Is there anything wrong?
Thanks so much,
Wei
Code: Select all
Design
;alts = alt1*, alt2*, nobuy
;rows = 24
;block = 3
;orth = ood
;model:

U(alt1) = b0 + b1 * Price[1.20, 3.26, 5.32, 7.38, 9.44, 11.50] +
               b2.dummy * CFI[0,1] +
               b3.dummy * Org[0,1] +
               b4.dummy * RFA[0,1] +
               b5 * CFI.dummy[1]*Org.dummy[1] +
               b6 * CFI.dummy[1]*RFA.dummy[1] +
               b7 * RFA.dummy[1]*Org.dummy[1] /
U(alt2) = b0 + b1 * Price +
               b2 * CFI +
               b3 * Org +
               b4 * RFA +
               b5 * CFI*Org +
               b6 * CFI*RFA +
               b7 * RFA*Org
     $
wxy008
 
Posts: 9
Joined: Wed Mar 04, 2020 3:22 am

Re: Problem of OOD design

Postby Michiel Bliemer » Sat Apr 04, 2020 10:32 am

I am not sure why it generates a D-optimality of 0%. OOD designs are tricky and sometimes the D-optimality measure as proposed by Street and Burgess gives 0% for no obvious reason. The D-error looks fine so there should be no issue using this design to estimate the coefficients. Note that OOD designs have limitations, for example they cannot remove dominant alternatives (so the * in the ;alts command will not work because OOD designs require an orthogonal design and do not allow removing choice tasks with a dominant alternative).

Instead, you could opt for a D-efficient design using ;eff = (mnl,d) with zero priors or small positive/negative priors in order toremove dominant alternatives.

Michiel
Michiel Bliemer
 
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Re: Problem of OOD design

Postby wxy008 » Sat Apr 04, 2020 11:56 pm

Michiel,

Thanks so much for your help. One more question, we mentioned that "The D-error looks fine", and how could you check the D-error in ood design? I did not find the place to check D-error on the result page displayed in Ngene.

Wei
wxy008
 
Posts: 9
Joined: Wed Mar 04, 2020 3:22 am

Re: Problem of OOD design

Postby Michiel Bliemer » Sun Apr 05, 2020 10:23 am

Tick the box "Design properties, MNL" on the left in the design output window.
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Posts: 898
Joined: Tue Mar 31, 2009 4:13 pm

Re: Problem of OOD design

Postby wxy008 » Mon Apr 06, 2020 12:36 am

Thanks so much. I really appreciate your help.

Wei
wxy008
 
Posts: 9
Joined: Wed Mar 04, 2020 3:22 am


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