I am trying to generate a new design for a DCE; please see the code below. The problem is that I get the warning "No valid design has been found after 1000 evaluations." I am recommended to check whether probabilities might be too extreme or priors too large. However, given the defined priors probabilities stay pretty close to 0.5 in all possible choice sets, as is visible in the design reported when I stop the search process. Letting the search process run for a long time does not help either.

Does anyone see the mistake I seem to be overlooking?

Best,

Christian

- Code: Select all
`Design`

;alts = alt_d, alt_g

;rows = 18

;block = 6

;eff = (mnl, d)

;model:

U(alt_d) = b1[-0.001] * WD[65,75,85]

+ b2.dummy[0.2] * C[1,2]

+ b3.dummy[0] * YD[1,2]

+ b4[0] * C.dummy[1]*YD.dummy[2]

+ b5[0] * C.dummy[2]*YD.dummy[1]

+ b6[0] * C.dummy[1]*YD.dummy[1]

/

U(alt_g) = b7[-0.001] * WG[65,75,85]

+ b8.dummy[0.3] * T[1,2]

+ b9.dummy[0] * YG[1,2]

+ b10[0] * T.dummy[1]*YG.dummy[2]

+ b11[0] * T.dummy[2]*YG.dummy[1]

+ b12[0] * T.dummy[1]*YG.dummy[1]

$