Searching for articles or insight on determining the number of vignettes needed for a study using the Factorial Survey Method.
This isn't a straightforward question to answer, but its really about the efficiency of allocation of vignettes and handling of the fractional design. With a 4x2 design you should be able to avoid aliasing of effects if you allocate reasonably efficiently.
I'd take a look at D efficiency and look to get an efficient allocation that way. Relying on random allocation is inefficient but might still be OK.
For example see:
Article Statistical modelling of vignette data in psychology
and the references in that paper.
I have 16 vignettes total, with two randomly selected for each survey participant using Qualtrics. I am trying to find guidance if two randomly selected out of sixteen is sufficient or if I should use more (e.g., four randomly selected out of 16).
You probably know this publication, but just in case you do not (Auspurg & Hinz 2015. Factorial Survey Experiments).
Do you plan on randomly drawing two vignettes from the vignette population for each participant, so that you end up with ratings for all vignettes after all? If that is the case, is it feasible (in terms of the time to complete your survey) that each respondent rates more than two vignettes?
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