Hi,
first the mathematics.
If you do this experiment ("A" or "B") 60 times, the probability that you get a result between 25/35 and 35/25 is about 94% with less 25/35 and more 29/31 and most 30/30.
That's Bernoulli.
Now some solutions:
1. The easiest at all:
Wait until both groups are filled. Remove randomly some respondents from the overquota group.
2. the easy ones:
You have two groups ("A" and "B").
a.You create a random number (1,2) with the relevance equations:
A : randnumber==1
B: randnumber==2
After one of the two groups is full (let's say A), you change the relevance equations to:
A : randnumber==0
B: (randnumber==1) OR (randnumber==2)
The same effect: You change the equation where you create your random number
from {if(is_empty(randnumber),rand(1,2),randnumber)}
to {2}.
b. You create a random number between 1 and 100
{if(is_empty(randnumber),rand(1,100),randnumber)}
Initially you set the relevance equations to
A : randnumber<51
B: randnumber>50
If you encounter a disbalance you can finetune to
A : randnumber<71
B: randnumber>30
So more respondents are thrown to group A.
Remember: This all is only a changing of text, which can be done while the survey is active.
3. Now the sophisiticated part, which will do this automatically. (if you have access to the database)
Use an ajax call and in the called php script query the database to find the least filled group.
Unfortunately the quota management of LimeSurvey is a bit simple. There is no access to something like "quota_target", "quota_Todo" or so.
Joffm
Volunteers are not paid.
Not because they are worthless, but because they are priceless
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