As you can see in the first code, I try to make sure when illness type=1 , sick= 0
In the design generated, type=1 only appear very limited times, much fewer than other types. I understand that as it is a constrained design, the level balance for nested attribute will be lost. Even adding (times of level requirements) after attribute will not work in this case.
However in this particular research, to make each respondent see more or less the same times of different types is necessary. The attribute level balance for "type" is desired.
Then in the second code, I randomly tried a way to "fix" this by adding another almost zero level for "sick" : sick[0, 0.0001, 50,100,150]
Somehow the design has balanced level for the attribute "type" now. If this works, I can easily treat sick=0.0001 as 0 in formatting questionnaires.
My question is, does this way of "fix" this problem really fix it? Will it cause other unintended problems? I do not see that for the moment, to me it seems the level of sick=0 and 0.0001 will have no or minimum effect on utility by the current utility function setting. But I am not sure.
I would appreciate a lot if there are other better ways to solve the problem.
Code: Select all
Design
;alts = alt1, alt2,alt3
;rows = 24
;eff=(mnl,d)
;block=3
;cond:
if(alt1.type=1,alt1.sick=[0]),
if(alt1.type<>1,alt1.sick>10),
if(alt2.type=1,alt2.sick=[0]),
if(alt2.type<>1,alt2.sick>10)
;model:
U(alt1)=b0[-0.5]
+b1[0.2|0.5|-0.2].effects*type[0,1,2,3]
+b2[0.01]*sick[0,50,100,150]
+b3[0.05]*die[5,10,20]
+b4[-0.015]*cost[20,50,100]
/
U(alt2)=b0+b1.effects*type+b2*sick+b3*die+b4*cost
$Code: Select all
Design
;alts = alt1, alt2,alt3
;rows = 24
;eff=(mnl,d)
;block=3
;cond:
if(alt1.type=1,alt1.sick=[0,0.0001]),
if(alt1.type<>1,alt1.sick>10),
if(alt2.type=1,alt2.sick=[0,0.0001]),
if(alt2.type<>1,alt2.sick>10)
;model:
U(alt1)=b0[-0.5]
+b1[0.2|0.5|-0.2].effects*type[0,1,2,3]
+b2[0.01]*sick[0,0.0001,50,100,150]
+b3[0.05]*die[5,10,20]
+b4[-0.015]*cost[20,50,100]
/
U(alt2)=b0+b1.effects*type+b2*sick+b3*die+b4*cost
$