Randomization of background colors

Question

How do I randomize a questionnaire so that half the participants get a questionnaire with a blue background color and the other half gets a questionnaire with the regular background color (white)

Answer 1

The easiest way was to put a placeholder in the layout where the background color is defined, something like this CSS code in the <style> section:

body {
    background-color: white;
    background-color: %experiment%;
}

And then to define the placeholder based on a random generator on the first page:

show('RG01')
if (value('RG01') == 1) {
  replace('%experiment%', '#FF9900');
} else {
  replace('%experiment%', '#0099FF');
}

Keep in mind, that the very last page, will not use this color.

Comments

HI, Thanks for your answer.
Does that mean, that I should have access to the php code directly? im afraid I am not authorized to make these changes. is there any other way to manage the change from the administration page.

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Sosci Survey intends to use PHP code in the questionnaire. Take a look here:
https://www.soscisurvey.de/help/doku.php/en:create:php

No special authorization required ;)