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Partial profile CBC with null level prohibitions

Hi Sawtooth  Software Team!

I am trying to design partial profile CBC with null level prohibitions and have been faced with a problem. My conjoint includes 23 attributes, each of them has null level. I am going to use partial profile design with 4 attributes shown in each concept and I want to be shown from 2 to 4 non-null levels in each concept.
My question is what numbers for minimum and maximum null levels per concept should I define in "Null level prohibitions" tab?

Many thanks in advance!
asked Apr 27, 2016 by Alexey Usankin

1 Answer

0 votes
OK, I just tried this out and it seems to work for me.


Minimum Null Levels Per Concept = 0
Maximum Null Levels Per Concept = 2
answered Apr 28, 2016 by Bryan Orme Platinum Sawtooth Software, Inc. (148,340 points)
Hi Brain!

I tried this evident option but it does not work with alert "The task could not be generated according to the constraints. Please check the prohibitions.". At least in SSI 6.4.6.

Meanwhile I found working adjustment (for 23 attributes in total and 4 attributes in partial profile with 2-4 non-null levels):
Minimum Null Levels Per Concept = 0
Maximum Null Levels Per Concept = 21

I just want to be sure that this is correct option for my design idea.
Well, I have to say I'm working in v9 and I don't have v6.4.6.  

Have you told the designer that you are using partial-profile with just 4 attributes shown per task?

I recommend after you generate a design that you think is working that you export it to the .CSV file, open it in Excel, and use some formulas in Excel to tabulate the min and max null levels per task across ALL tasks in your design.  That way you can really know what will be shown across all respondents and all versions.  If you find that you cannot get v6.4.6 to do the null level prohibitions correctly for you for this situation, know that you can do some editing to the design file you've exported to .CSV to remedy your design...then import back into SSI Web...then run test design again to make sure that the design efficiency statistics haven't moved much from what the software originally generated.
Thanks a lot!
I have checked every task to ascertain that there are from 2 to 4 non-null levels in each concept. I just want to confirm that these options (0-21) are valid approach for my idea.
Well, if it works, it works!  Glad you exported the design and verified that you're getting what you want in your partial-profile tasks...and always make sure to test your design.