Constraing and dominant alternative

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Constraing and dominant alternative

Postby jaein.seo » Tue Dec 04, 2018 6:56 am

Hello,

I'm writing to ask a question why the code does not run with * for an alternative.
I have 5 attributes and 2 constraints. I wanted to avoid pairing 0, 1 of attribute B with 2, 3 of attribute A.
I ran the following code and didn't run. So I removed * from altB and it started running immediately. I'd like to know why it's the case and if there's another way to prevent from having attribute level dominance.

Code: Select all
Design
;alts = altA*,altB*, none

;rows = 36
;block = 3

;eff  = (mnl,d)
;alg  = swap(stop=total(600mins))

;cond:
if(altA.B <>2, altA.A = [0,1]),
if(altB.B <>2, altB.A = [0,1])

;model:
U(trtA)=b01[0] +
       b1.dummy[0|0|0]        *A[3,2,1,0] +
       b2.dummy[0.02|0.01]  *B[2,1,0]   +
       b3.dummy[0.02|0.01]  *C[2,1,0]   +
       b4.dummy[0|0]           *D[2,1,0]   +
       b5[-0.01]                     *E[0,1,2,3] /

U(trtB)=b02[0] +
       b1                   *A +
       b2                   *B +
       b3                   *C +
       b4                   *D +
       b5                   *E $


Thank you for your time reviewing.
jaein.seo
 
Posts: 9
Joined: Sat Nov 04, 2017 12:08 am

Re: Constraing and dominant alternative

Postby Michiel Bliemer » Tue Dec 04, 2018 8:29 am

You only specified non-zero priors for attributes B and C, so Ngene will ignore the other attributes when looking for dominant alternatives. There are only 9 possible combinations of attribute levels B and C, and most of them will have a dominant alternative. Further, you rule out some attribute level combinations for B as well, therefore there are hardly any combinations left while you are asking for 36 rows without any dominant alternatives.

The solution is to set priors for A, D, and E as well. Another solution is to decrease the number of rows.

Note that you need to use altA and altB in your utility specifications instead of trtA and trtB.

Michiel
Michiel Bliemer
 
Posts: 1705
Joined: Tue Mar 31, 2009 4:13 pm


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