Millisecond Forums

How do I both randomize the order in which my trials appear and set the number of "correct" response trials that should appear during my experiment?

https://forums.millisecond.com/Topic27496.aspx

By psychnewbie - 7/23/2019

I'm working on a version of a GNAT, and the project's PI wants to be able to specifically set the number of "correct pairs" (or pairs of images that are designated as requiring the press of a space bar) that participants are shown. How can I do this while also randomizing the order in which participants see trials?
By Dave - 7/23/2019

psychnewbie - 7/23/2019
I'm working on a version of a GNAT, and the project's PI wants to be able to specifically set the number of "correct pairs" (or pairs of images that are designated as requiring the press of a space bar) that participants are shown. How can I do this while also randomizing the order in which participants see trials?

There isn't sufficient information here to give a response. Ordinarily, you simply create two <trial> elements -- one that displays a "correct pair" and thus requires a response, another one that doesn't -- and then you randomize their order via the <block>'s /trials attribute.
By psychnewbie - 7/23/2019

Dave - 7/23/2019
psychnewbie - 7/23/2019
I'm working on a version of a GNAT, and the project's PI wants to be able to specifically set the number of "correct pairs" (or pairs of images that are designated as requiring the press of a space bar) that participants are shown. How can I do this while also randomizing the order in which participants see trials?

There isn't sufficient information here to give a response. Ordinarily, you simply create two <trial> elements -- one that displays a "correct pair" and thus requires a response, another one that doesn't -- and then you randomize their order via the <block>'s /trials attribute.

I've done that, but is there any way to (for example) specify that within a block of 50 trials, the "correct pair" trial appears 30 times? Or is that not compatible with randomizing trials within blocks?
By Dave - 7/23/2019

psychnewbie - 7/23/2019
Dave - 7/23/2019
psychnewbie - 7/23/2019
I'm working on a version of a GNAT, and the project's PI wants to be able to specifically set the number of "correct pairs" (or pairs of images that are designated as requiring the press of a space bar) that participants are shown. How can I do this while also randomizing the order in which participants see trials?

There isn't sufficient information here to give a response. Ordinarily, you simply create two <trial> elements -- one that displays a "correct pair" and thus requires a response, another one that doesn't -- and then you randomize their order via the <block>'s /trials attribute.

I've done that, but is there any way to (for example) specify that within a block of 50 trials, the "correct pair" trial appears 30 times? Or is that not compatible with randomizing trials within blocks?

That's perfectly possible. You simply enter the trials in the desired proportions into the noreplace() selection pool in the <block>'s /trials attribute.

/ trials = [1 - 50 = noreplace(correct_pair, correct_pair, correct_pair, incorrect_pair, incorrect_pair)]

will run exactly 30 instances of <trial correct_pair> and 20 instances of <trial incorrect_pair> in random order, i.e. a 3:2 ratio.