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Experimental randomisation

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5 years 4 months ago #186212 by VickyLyonEPP
Experimental randomisation was created by VickyLyonEPP
Hi!
I'm trying to create a survey that will randomly attribute each participant to one of four groups. Each group should then view a different stimuli (text). The rest of the survey should be the same for everyone.

As far as I can tell, the randomization function allows us to present the questions in a random order, but not to create separate groups? Is there any way to do this? I'm very unfamiliar with limesurvey, so any help would be much appreciated.

Thank you!!
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5 years 4 months ago #186220 by tpartner
Replied by tpartner on topic Experimental randomisation
You will need to load a hidden (via CSS) equation question with a random number 1-4 and then place relevance/conditions on your "stimuli" questions based on the hidden random number.

Cheers,
Tony Partner

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5 years 4 months ago #186222 by VickyLyonEPP
Replied by VickyLyonEPP on topic Experimental randomisation
Thank you for your reply! Is there any place I can learn how to do this? A walk through, tutorial, video...? I've been trying to read the manual but it's very confusing!
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5 years 4 months ago #186237 by VickyLyonEPP
Replied by VickyLyonEPP on topic Experimental randomisation
I found another question about this and followed the instructions:
create a question of type "equation" (question code? let's say "randomnumber")

question text: {if(!is_empty(randomnumber),rand(1,2,3,4),randomnumber)}

Question 1, relevance equation: "randomnumber==1"
Question 2, relevance equation: "randomnumber==2"
Question 3, relevance equation: "randomnumber==3"
Question 4, relevance equation: "randomnumber==4"

However the randomized question doesn't show up when I preview the survey. Does anyone have any idea of what I'm doing wrong?
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5 years 4 months ago #186239 by tpartner
Replied by tpartner on topic Experimental randomisation
The equation question text should be:

Code:
{if(!is_empty(randomnumber), rand(1,4), randomnumber)}

- www.limesurvey.org/manual/Expression_Man...#Access_to_Functions

Cheers,
Tony Partner

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5 years 4 months ago - 5 years 4 months ago #186240 by VickyLyonEPP
Replied by VickyLyonEPP on topic Experimental randomisation
Thank you! makes sense! however I still dont see the randomized questions showing up. Is there something I'm missing? Something to activate in the settings maybe?

Edit: I unhid the equation question but don't see any number show up when I preview. Is that normal?
Last edit: 5 years 4 months ago by VickyLyonEPP.
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5 years 4 months ago #186241 by tpartner
Replied by tpartner on topic Experimental randomisation
No, can you attach a small sample survey (.lss file) containing only the relevant questions?

Cheers,
Tony Partner

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5 years 4 months ago - 5 years 4 months ago #186243 by VickyLyonEPP
Replied by VickyLyonEPP on topic Experimental randomisation
Here is the .lss, I removed all the other questions

File Attachment:

File Name: limesurvey...9241.lss
File Size:20 KB
Last edit: 5 years 4 months ago by VickyLyonEPP.
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5 years 4 months ago #186245 by VickyLyonEPP
Replied by VickyLyonEPP on topic Experimental randomisation
I replaced
{if(!is_empty(randomnumber), rand(1,4), randomnumber)}
by
{rand(1,4)}
It works!
However, I haven't hidden that question yet, and while testing, I noticed that when I saw the number that showed up didn't always match the question it was assigned to (eg I saw the number 3 but the question that showed up was assigned randomnumber==1 )
I hope this is normal?
Thank you very much for you time in any case!
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5 years 4 months ago #186246 by VickyLyonEPP
Replied by VickyLyonEPP on topic Experimental randomisation
I do just have a final question though, I've tried it again and though the questions do show up randomly, the number that showed up didn't always match the question it was assigned to (eg I saw the number 3 but the question that showed up was assigned randomnumber==1 ).
In that case, how can I know which question the participants saw when I do the data analysis?
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5 years 4 months ago #186255 by tpartner
Replied by tpartner on topic Experimental randomisation
It's because Expression Manager sets the equation question both on page load and submit - that's why you put the IF statement in so the equation question is only loaded if it's empty.

Having said that, you had some unnecessary HTML and a typo in the equation question.

It should be:

Code:
{if(is_empty(randomnumber), rand(1,4), randomnumber)}

Working sample survey attached:

File Attachment:

File Name: limesurvey...9924.lss
File Size:20 KB

Cheers,
Tony Partner

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5 years 4 months ago #186262 by DenisChenu
Replied by DenisChenu on topic Experimental randomisation

tpartner wrote: Having said that, you had some unnecessary HTML and a typo in the equation question.

:)

It's the reason of www.limesurvey.org/manual/Question_type_...ation_.28equation.29

clean textarea without HTML editor : less chance to add broken html :)

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