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How to determine which batch or expt was run based on subject id or group id


How to determine which batch or expt was run based on subject id or...
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seandr
seandr
seandr
posted 10 Years Ago
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Inquisit allows you to perform between-subject manipulations at the <batch> or <expt> level using the / subjects attribute. For example, the following varies the order of the script based on groupid:

<batch>
/ subjects = (1 of 2)
/ groupassignment = groupnumber
/file="foo.iqx"
/file="bar.iqx"
</batch>

<batch>
/ subjects = (2 of 2)
/ groupassignment = groupnumber
/file="bar.iqx"
/file="foo.iqx"
</batch>

When the experiment runs, Inquisit assigns a participant to one or the other <batch> based on the group id, which, depending on configuration, could be a randomly or sequentially generated number, or something entered by the researcher or the participant. Let's say the group id was a randomly generated value of 18843245. How do you determine which <batch> that group id value corresponds to? 

This can be determined with the following formula:

group = ((groupid - 1) % groupcount) + 1

where groupcount is the total number of groups (2 in the above example) and % represents the modulus operator, which returns the remainder after the numerator is divided by the denominator. If we plug the values from our example into the formula, we get:

group = ((18843245 - 1) % 2) + 1

which is equal to 1. In other words, this particular participant ran group 1, where foo.iqx was administered first and bar.iqx was administered second. If /groupassigment = subjectnumber or is unassigned, we would use the same formula but plug in the subject id rather than the group id. 

When analyzing your data, you'll want to calculate a group variable using this formula in order to test or control for order effects or other between-subject manipulations. If you are using Microsoft Excel, the formula is "=MOD(A2-1, 4) +1" where A2 is the cell that has the subject or group id.

Edited 10 Years Ago by seandr
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How to determine which batch or expt was run based on subject id or...
seandr - 10 Years Ago
     + x [quote] [b] seandr - Friday, July 25, 2014 [/b] Just...
hollysully - 7 Years Ago
             + x [quote] [b] hollysully - Thursday, August 31, 2017 [/b]...
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