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How to randomly assign the sample in two groups and have different CBCExercises displayed for each

I would like to have two randomly assigned groups that go through my questionnaire with 3 CBC sets each.
The only difference between the sets is that one group has a set of 4 products and the other group has a set of 6 products displayed. However, the follow up questions are identical for both groups.

I have already created two versions for each CBC ( a short version with 4 products and a regular with 6 products). So once you are randomly assigned to e.g. group 1, you should always have only 4 products displayed in all 3  CBCs, and if assigned to group 2, always 6.

How can I implement this?
Do I create 2 separate questionnaires or is there a way to incorporate them into one?

Thank you!
asked Nov 25, 2019 by anonymous

1 Answer

0 votes
I don't see any reason you couldn't do this with one questionnaire if you want to.

To split the respondents, you'll likely want to use a quota question.  You could give the quota two cells, both set to always qualify.  Then if you randomize the quota cell order and set the quota to use least fill, you should end up with a fairly 50:50 split.

After that, it's just a matter of adding skips to your questionnaire.  On whatever question comes before the CBCs, you can add skips that skip some respondents to the first CBC and some to the second, using logic like "QuotaQ = 1" and "QuotaQ = 2" (where "QuotaQ" is the name of the quota question, and the 1 / 2 are the cell values in the quota question).  Then, at the end of the CBCs, you can add skips to bring all respondents back to the follow-up questions.

Note that Lighthouse Studio doesn't allow you to actually skip directly to or from a CBC question.  If you add a text question to the same page, you should be able to use that for your skips instead of the CBC questions themselves.
answered Nov 25, 2019 by Zachary Platinum Sawtooth Software, Inc. (147,200 points)
Thank you very much for your quick response, Zachary.

You mentioned to randomize the quota cell order - where do I do this or does it do so automatically?

Everything else works perfectly fine now. Thanks alot!
I don't know what version of SSI Web / Lighthouse Studio you are running, but in Lighthouse Studio 9.8.0, there's a dropdown labelled "Check for cell membership method" in the quota question's first tab.

I may have misspoke.  There's a randomize option in that dropdown, but you probably want to use least fill instead.  Least fill tries to put respondents into the most empty cell and has random tiebreakers baked in.
Thank you!!