Hi all,

I'm working on CBC (Choice-Based Conjoint) studies and my problem today (in 
fact, it's a problem I have since so many days ;) is how to generate a balanced 
design of experiments for that kind of study.

Here is the background of my study (based on an example) :

I have 3 variables X, Y and Z. Each could take respectively 2, 3 and 3 levels. I 
have 500 respondents.
All of them see 3 tasks of 4 products (I remind you that a product is a 
combination of levels of each variable).
Then, I want to program the generation of the design of experiments for such a 
case.


The design of experiments should verify two conditions :

1/ Each task should not have two identical products, and each respondent should 
not see two identical tasks (and all respondents don't see the same tasks).

2/ Each respondent should see the same number of times each possible combination 
of levels of two variables.

My major issue is how to have this second condition. 

In fact, I've seen that the Fedorov algorithm is often used in order to generate 
design of experiments for CBC but with the "optFederov" function (of the 
"AlgDesign" package), I haven't be able to obtain such a balanced design of 
experiments...
So, I thought to program it myself (in R or may be in an other language, I don't 
know yet) but I'm afraid it would be complicated and mostly not very effective 
to check all the possible combinations of levels of two variables.


I hope my message is not too confused, and if you have any clue of how to 
program the generation of design of experiments in such a case, I would be very 
grateful.

Thanks :)


Aline Deschamps
Nantes, France

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