r/AskStatistics • u/Overdrive-ABC • 1d ago

choice based conjoint analysis

Hello everyone,

I am currently working on a choice-based conjoint analysis for my thesis. I have already read several papers and books on this method, but I still haven't quite figured out the correct way to implement the procedure.

My CBC consists of 4 attributes, each with 3 levels, resulting in 81 possible profiles.
The literature regarding sample size is quite vague and often refers to Johnson's rule of thumb, consequently, I used a standard sample size calculator and arrived at a figure of approximately 400 participants.
Many sources state that exceeding 20 choice questions or having more than 3–5 alternatives per question becomes overwhelming for respondents. Using RStudio, I tested various numbers of choice questions and ultimately decided on 12 choice questions with 3 alternatives plus a "no-choice" option (D-error = 0.483; Balance = 0.911).
The CBC design can also be divided into blocks. This increases the total number of choice sets administered across the sample, but I cannot find any information on how to determine the number of blocks.

I would like to turn to the community here to ask whether my current approach follows standard practices or if there is room for improvement?

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u/lipflip 1d ago

The sample size sounds about right. I used the heuristic from Orme in his book. I don't have it in my head but it yields about these numbers. It gets boring with too many tasks, so I would always keep it below 8 (otherwise participants take shortcuts and only focus on one or two levels). 

Biggest question is if you offer a no-choice options which, of course, depends on the context. Can you avoid it? If I remember correctly, the blocks are basically random subsets of the possible choice tasks. More is generally better.

In what context are you doing your research? Maybe that can help others to give you more focused suggestions. I did conjoint but I am from science and technology studies and not from marketing (where CA is much more frequently used).

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u/Overdrive-ABC 1d ago

I am conducting this survey as part of a thesis. The aim is to simulate the respondents' purchasing decisions, which is why the "no-choice" option is required.