Please help us help you and fill where relevant:
Your LimeSurvey version: 3.28.34
Own server or LimeSurvey hosting: LimeSurvey
Survey theme/template:extends_vanilla
==================
Dear LimeSurvey Team,

For my survey I need a certain design of a study and I have a question regarding random order of the questions. My survey will have 24 choice tasks but to test the responders understanding and focus I want to divide the 24 choice tasks with additional "responders check" question after first eight questions and second eight questions. How such survey can be designed? If I divide them into 3 groups randomly choosing 8 out of 24 questions, there is a risk of duplicating them.

BR,
Aleksandra

Give the same randomisation group name to all 24 questions.
After the 8. and after the 16. question insert your additional questions.

How do you want to display?
"question by question", "group by group"?

Joffm 

Thank You very much for the answer! I want to display "question by question". Applying same randomization group will prevent duplicating the questions in second and third "eight questions" parts?

Read the manual about it.
[url] manual.limesurvey.org/Question_type_-_Li...e_.28random_group.29 [/url]

So how can they be duplicated? We only talk about "random order".

Joffm

Ok, now I see. It does not matter if the questions will be displayed divided by the "responders check" questions. If they be in the same randomization group they will be displayed randomly.

Yes, the 24 questions will be distributed randomly over the 24 slots for those questions in the same randomization group. It doesn't matter where those slots are. They don't need to be consecutive. You could for example display 12 at the beginning and 12 at the end. The only thing LS will do is to shuffle the questions around between the different positions defined via the same randomization group name.

Thank You very much! I have additional question - is it possible to retrieve in the results exported from questionnaire the order in which questions were displayed?

You can use Qcode.qseq to get the question position.

- manual.limesurvey.org/ExpressionScript_-...#Access_to_variables

I checked the manual but I am not sure where should I include the code. Can You please give me more details on that?

In a question of type "equation".
E.g. you may use the "list" function
manual.limesurvey.org/ExpressionScript_-...mplemented_functions
like
{list(Q1.qseq,Q2.qseq,...)}

Joffm