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I assist with a nonprofit that conducts votes during a meeting.  1 person per group will submit a vote.  The group voting may have between 1 and 20 people in it.  The voting questions are all answered as Yes/No.  I will know the group size before-hand, but the group sizes will vary in a single event/survey.  

Can I use LimeSurvey with usernames and specify a group quantity? This group quantity would then translate to a total number of yes/no votes on each question in a survey.  

Example:
User_A: 5 group members
User_B: 12 group members

Question 1: Is pizza the best food ever? 
User_A would have to submit a combination of 5 yes and/or no votes for their group.
User_B would have to submit a combination of 12 yes and/or no votes for their group. 
No partial votes (i.e. User_A can't submit 2 yes or no, must submit all 5)

Repeat for any additional questions needed.  

Hi,

Can I use LimeSurvey with usernames and specify a group quantity?

Use a token based survey and specify the group quantity in an additional attribute

Question 1: Is pizza the best food ever? 
User_A would have to submit a combination of 5 yes and/or no votes for their group.

So there is ONE member of the group who enters ALL responses of the group?

So either you can use a question of type array.
Display as many rows as there are memers (subquestion relevance)
Here each question is answered for all group members iúntil the next question is displáyed.
Questions are not mandatory but you validate that all members answered.
validation equation like "count(self)==TOKEN:ATTRIBUTE_1

or you can create as many groups with all questions as there are members in your groups.
Display as many groups as there are group members by "condition".
Questions are mandatory.

Joffm