I think you can use the randomizer to do what you want to, but it takes 2 steps to accomplish it: either a randomizer in the survey flow and randomization on a survey block (Qualtrics yells at you about the nested logic, though it seems to work, but that doesn't give you question timing options) or two randomizers, one to set which content should be seen and one to put all the content in front of the respondent in randomized order).
You have 14 static questions # 1-14 for all respondents
You have 40 variable questions #15-55 of which 14 will be shown.
UPDATED: put each question on its own block, and put a timing question (not displayed to the respondent) in the block with it. This will give you the ability to time each question.

• Go to survey flow


• Create a separate embedded data step for each of the variable questions (eg Q15=Show, Q16=Show, Q17=Show) [sorry in my screen shot I just used Q1,Q2,Q3 but the hopefully you get the idea)


• Put the 40 separate embedded data steps into a randomizer step, and set it to show 14 of them. Qualtrics will randomly select 14 of the fields to "Show" - now you have something to use to present the content later.


• Move the randomizing to the TOP of the survey, before a single thing has been shown the respondent. The survey has already determined what they will see, but now you can lay it out as you desire.


• Below the randomizer that is determining order, create a new randomizer that includes the separate blocks for each question. The static question blocks can simply be placed in there; for the variable questions, use branch logic to determine if they are seen or not (show the block with Q15 if Q15 = Show, show the block with Q16 if Q16=Show) etc.



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