By YL - 11/27/2017
Hi, how do I set up in a block attribute that a fixed number of trials are selected from each trial type but are randomly presented within a block?
Thanks!
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By Dave - 11/27/2017
+xHi, how do I set up in a block attribute that a fixed number of trials are selected from each trial type but are randomly presented within a block? Thanks!
You do so via the <block>'s /trials attribute and a noreplace() selection pool. Note that you need to enter the trials into the noreplace() pool in the desired proportions.
<block example>
/ trials = [1-30 = noreplace(a,b)]
</block>
will result in 15 "a" trials and 15 "b" trials -- equal proportions -- in random order.
<block example>
/ trials = [1-30 = noreplace(a,a,b)]
</block>
will result in 20 "a" trials and only 10 "b" trials -- a 2:1 ratio -- in random order.
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