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noreplace unequal categories

olciak — Tue, 01 Apr 2014 17:06:02 GMT

Hello,
I'm recently working on the procedure in which I have to display items without replacement from unequal categories. qFURNITURE_S has 2 items, qFURNITURE_M has 3 items and qFURNITURE_W has 5 items.
I tried noreplace and noreplacenorepeat command and both of them don't work (so some of the items are displayed more than once). Also at the trial level I used both commands (noreplace and noreplacenorepeat ) to make them unrepeatable. Below I pasted the part of the script.
Thanks for your help in advance.
<block FURNITURE>
/trials = [1=firstFURNITURE; 2-11=noreplacenorepeat(qFURNITURE_S,qFURNITURE_M,qFURNITURE_W)]
/bgstim = (categorization,FURNITUREhead)
</block>

RE: noreplace unequal categories

olciak — Tue, 01 Apr 2014 17:06:02 GMT

Thank you very much for your replay!
Best,
Olga

RE: noreplace unequal categories

Dave — Tue, 01 Apr 2014 16:57:28 GMT

/ trials = [1-8=noreplace(a,b)]

means sample trials a and b in equal proportions. You'll end up with 4 a-trials and 4-b-trials in random order. With

/ trials = [1-9=noreplace(a,a,b)]

you'll end up with twice as many a-trials compared to b-trials; there'll be 6 x a and only 3 x b, again in random order.

The same applies to your situation: You ought to enter trials in the selection pool in the proportions you need. You'll also find this covered in the documentation topic for the /trials attribute and its examples:

The following block randomly selects either testtrial or distractortrial for each of its 12 trials. The testtrial is run exactly 8 time and distractortrial is run 4 times.

<block myblock>
/ trials=[1-12=noreplace(testtrial, testtrial, distractortrial)]
</block>