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Check Randomization
- dgiacometti
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7 years 4 weeks ago #148858
by dgiacometti
Check Randomization was created by dgiacometti
Dear all,
I've performed some test and it appears that the randomization does not work.
I want to randomize in half participants to two different question groups.
I created a hidden question (equation type) using the following string:
{if(is_empty(Q1),floor(rand(1,2)),Q1)}
So it should randomize in half since the condition is Q1 == 1 for the first group and Q1 == 2 for the second.
I did some tests and in one case I had 6 (1) and 4 (2) (for this I set the quota at 10) and in the other 3 (1) and 7 (1).
Does the IP address have any influence on this?
I will have 100 participants in my survey. How can I be sure that they are split 50% in each question group?
Thank you very much in advance.
Dg
I've performed some test and it appears that the randomization does not work.
I want to randomize in half participants to two different question groups.
I created a hidden question (equation type) using the following string:
{if(is_empty(Q1),floor(rand(1,2)),Q1)}
So it should randomize in half since the condition is Q1 == 1 for the first group and Q1 == 2 for the second.
I did some tests and in one case I had 6 (1) and 4 (2) (for this I set the quota at 10) and in the other 3 (1) and 7 (1).
Does the IP address have any influence on this?
I will have 100 participants in my survey. How can I be sure that they are split 50% in each question group?
Thank you very much in advance.
Dg
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- jelo
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7 years 4 weeks ago #148865
by jelo
So 6:4 after 10 runs won't translate into 60:40 after 100 runs.
Some allow to override randomization partially and let you edit the counts.
www.qualtrics.com/support/survey-platfor...mizer/#EditingCounts
When you only have two groups to assign, you could use the saveid/response id of every interview.
That is always odd/even. But you still often don't end up with 50:50 after 100 runs. That's because people reload the browser or stop during the survey.
If you already know your exact 100 respondents, you can use tokens and attributes to assign the question groups upfront.
I wouldn't spent that much time on a exact split. These excact split demands normally pop up from university tasks. Which is a bit confusing, since demanding 50:50 split during a field phase means you count every completed response afterwards. Even if the content is nonsense (which happens online from time to time
The meaning of the word "stable" for users
www.limesurvey.org/forum/development/117...ord-stable-for-users
Replied by jelo on topic Check Randomization
Your randomization is working fine. A test consisting of 10 tries won't always be 5:5.dgiacometti wrote: I did some tests and in one case I had 6 (1) and 4 (2) (for this I set the quota at 10) and in the other 3 (1) and 7 (1).
So 6:4 after 10 runs won't translate into 60:40 after 100 runs.
Currently there is no way to ensure that 100%, because what's with situations like when the respondent quits the survey during the interview? LS would need to tap into the complete responses to decide which group should be assign the next respondents. There are survey packages which can do these things. But I am not aware of a surveytool that ensures 100% even distribution among the randomized sections. Some tools e.g. qualtics allows you to change the distribution during the survey.dgiacometti wrote: I will have 100 participants in my survey. How can I be sure that they are split 50% in each question group?
Some allow to override randomization partially and let you edit the counts.
www.qualtrics.com/support/survey-platfor...mizer/#EditingCounts
When you only have two groups to assign, you could use the saveid/response id of every interview.
That is always odd/even. But you still often don't end up with 50:50 after 100 runs. That's because people reload the browser or stop during the survey.
If you already know your exact 100 respondents, you can use tokens and attributes to assign the question groups upfront.
I wouldn't spent that much time on a exact split. These excact split demands normally pop up from university tasks. Which is a bit confusing, since demanding 50:50 split during a field phase means you count every completed response afterwards. Even if the content is nonsense (which happens online from time to time
The meaning of the word "stable" for users
www.limesurvey.org/forum/development/117...ord-stable-for-users
The following user(s) said Thank You: dgiacometti
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- dgiacometti
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7 years 4 weeks ago #148867
by dgiacometti
Replied by dgiacometti on topic Check Randomization
Thank you very much for very detailed and useful explanation.
What are the passages I have to do to in the platform to assign tokens to question groups?
In that case I would not need anymore the equation randomization question at the beginning? Right?
Thank you again.
Bests,
Dg
What are the passages I have to do to in the platform to assign tokens to question groups?
In that case I would not need anymore the equation randomization question at the beginning? Right?
Thank you again.
Bests,
Dg
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- jelo
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7 years 3 weeks ago #148872
by jelo
You can uses tokens. Which means that you provide e.g. a invitation link to your respondents. This link includes a token. In Limesurvey you can add attributes to every token.
manual.limesurvey.org/Survey_participant...ned_attribute_fields
You e.g. add group as a attribute to your tokenlist. Next step would be to enter a value for this attribute for every token. So you will end up with 50% with group=1 and 50% with group=2
In Limesurvey you then can access this token attribute group via conditions. You then can display/hide a questiongroup depending on the value group=1 or group=2.
Sounds a bit complicated but once you got uses to tokens you will see that it is not that much work.
The main question to answer first is if you really able to contact every potential respondent and provide them a token/invitation link.
The meaning of the word "stable" for users
www.limesurvey.org/forum/development/117...ord-stable-for-users
Replied by jelo on topic Check Randomization
You're not assigning tokens to questions groups directly.dgiacometti wrote: What are the passages I have to do to in the platform to assign tokens to question groups?
You can uses tokens. Which means that you provide e.g. a invitation link to your respondents. This link includes a token. In Limesurvey you can add attributes to every token.
manual.limesurvey.org/Survey_participant...ned_attribute_fields
You e.g. add group as a attribute to your tokenlist. Next step would be to enter a value for this attribute for every token. So you will end up with 50% with group=1 and 50% with group=2
In Limesurvey you then can access this token attribute group via conditions. You then can display/hide a questiongroup depending on the value group=1 or group=2.
Sounds a bit complicated but once you got uses to tokens you will see that it is not that much work.
The main question to answer first is if you really able to contact every potential respondent and provide them a token/invitation link.
The meaning of the word "stable" for users
www.limesurvey.org/forum/development/117...ord-stable-for-users
The following user(s) said Thank You: dgiacometti
The topic has been locked.
- holch
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7 years 3 weeks ago #148939
by holch
I answer at the LimeSurvey forum in my spare time, I'm not a LimeSurvey GmbH employee.
No support via private message.
Replied by holch on topic Check Randomization
As Jelo said, randomization doesn't work like this...
If you have a random number between of either 1 or 2, for each draw there is a 50% chance to get one or the other. However, it does not mean that at the end you will have 50% "1" and 50% "2", this is not how chance works.
The larger the number of draws, the closer to a 50/50 distribution you should get, but it hardly ever is 50/50. n=10 is definitely not a large number and even n=100 I wouldn't consider a large number. With n=1000 chances are night that you get relatively close to a 50/50 distribution. Important is the word "close".
If you need 50 in one and 50 in another case, it is best to follow Jelos recomendation of distributing the case for each participant beforehand in the token table as custom attribute. But even there is no guarantee that you will end up with 50 for each case, only if really everyone of the sample answers.
If you have a random number between of either 1 or 2, for each draw there is a 50% chance to get one or the other. However, it does not mean that at the end you will have 50% "1" and 50% "2", this is not how chance works.
The larger the number of draws, the closer to a 50/50 distribution you should get, but it hardly ever is 50/50. n=10 is definitely not a large number and even n=100 I wouldn't consider a large number. With n=1000 chances are night that you get relatively close to a 50/50 distribution. Important is the word "close".
If you need 50 in one and 50 in another case, it is best to follow Jelos recomendation of distributing the case for each participant beforehand in the token table as custom attribute. But even there is no guarantee that you will end up with 50 for each case, only if really everyone of the sample answers.
I answer at the LimeSurvey forum in my spare time, I'm not a LimeSurvey GmbH employee.
No support via private message.
The topic has been locked.