Webstudy: Allocation of subjects to conditions

mariela — Mon, 13 Jul 2015 04:36:19 GMT

Hi,
i am currently setting up an experiment that I would like to conduct online. In this experiment I have 3 conditions (between).
In a lab study I would assign participants by their subject id to the different conditions.

<expt I>
/ blocks = [1= ...]
/ subjects = (1 of 3)
</expt>

<expt II>
/ blocks = [1= ...]
/ subjects = (2 of 3)
</expt>

<expt III>
/ blocks = [1= ...]
/ subjects = (3 of 3)
</expt>

How can I allocate subjects to conditions in an online study where I am not able to type in the subject ID manually?
I would rather not want to provide different links to the same study, as I am using an online platform an participants could then participate several times in the study ...

Thanks for your help,
mariela

RE: Webstudy: Allocation of subjects to conditions

Dave — Mon, 13 Jul 2015 04:36:19 GMT

The options are

(1) Have the launch page generate subject numbers randomly or sequentially. Assignment of a given participant to a given condition will be random (in latter case determine by when a given participant visits the launch page).
(2) Pass the subject number in to the launch page via a URL query parameter.

You could also consider assigning not by subject number, but using group number instead, i.e.

<expt>
/ subjects = (1 of 3)
/ groupassignment = groupnumber
...
</expt>

...

The above options (random generation of group number, passing it in via query parameter) apply as well.

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Webstudy: Allocation of subjects to conditions

RE: Webstudy: Allocation of subjects to conditions