Randomization of items with different set sizes without repetition and equal amounts of display...


Randomization of items with different set sizes without repetition and...
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mongrel
mongrel
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Hello again,

again... a beginner's question:

I have four item sets:

1. 10 different geometric forms (form 1-10)
2. 10 different numbers (number 1-10)
3. 10 different pictures (haus 1-10)
4. 1 picture that I want to be represented 10 times (SetA9Y1)

I would like to randomise all items without repetition. What I did so far is the following:

<block primingSetA9Y1>
     /trials = [1-40=noreplacenorepeat(Zahl1, Zahl2, Zahl3, Zahl4,Zahl5,Zahl6,Zahl7,Zahl8,Zahl9,Zahl10,
     Form1, Form2, Form3, Form4,Form5,Form6,Form7,Form8,Form9,Form10, haus1, haus2, haus3,
     haus4,haus5,haus6,haus7,haus8,haus9,haus10, SetA9Y1, SetA9Y1, SetA9Y1, SetA9Y1, SetA9Y1, SetA9Y1, SetA9Y1,
     SetA9Y1, SetA9Y1, SetA9Y1)]
    </block>

I "pretended" SetA9Y1 are 10 different stimuli in order to make sure, the stimulus is presented 10 times. Obviously, the norepeat attribute is not working because Inquisit views SetA9Y1 and SetA9Y1 as different stimuli. However, I do not want SetA9Y1 to be repeated right after SetA9... How can I solve this dilemma?

Thank you very much in advance!

M.


Dave
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Setting up separate a separate <trial> for each geometric form, each number, and each building seems inefficient.

You only need four <trial> elements:
(1)
<trial form>
/ stimulusframes = [1=formen]
...
</trial>

<picture formen>
/ items = ("form1.jpg", "form2.jpg", "form3.jpg", ...., "form10.jpg")
...
</picture>

(2)
<trial zahl>
/ stimulusframes = [1=zahlen]
...
</trial>

<text zahlen>
/ items = ("1", "2", "3", ...., "10")
...
</text>

(3)
<trial haus>
/ stimulusframes = [1=haeuser]
...
</trial>

<picture haeuser>
/ items = ("haus1.jpg", "haus2.jpg", "haus3.jpg", ...., "haus10.jpg")
...
</picture>

and

(4)
<trial SetA9Y1>
/ stimulusframes = [1=seta9y1pic]
...
</trial>

<picture seta9y1pic>
/ items = ("seta9y1.jpg")
...
</picture>

Then you can simply do:

<block primingSetA9Y1>
     /trials = [1-40=noreplacenorepeat(zahl, form, haus, SetA9Y1)]
    </block>
mongrel
mongrel
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Hi Dave,

Thank you for your quick reply.
I have two more questions:

1. If one trial contains 10 items and another trial contains only one item and I randomise those, is it guaranteed that the single item of the latter trial is represented as often as each item of the first trial?

2. I always thaught that the randomization of trials in a block leads to a randomization across all trials, but not across the items. In the end, I want the items to be displayed like this for example: Form5, SetA9Y1, Haus7, SetA9Y1, From4, Zahl10, Haus3, Zahl2, SetA9Y1... I do not want a randimization only within the trials, which would look like this Form10, Form2, Form8..., Haus3, Haus9, Haus10...., Zahl2, Zahl5, Zahl1....etc. And that is what I would suspect to happen, if I use your suggestion. Am I wrong? And if not, how can I display the items the way I want them to be displayed?

Thank you very much!

M.



Dave
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"1. If one trial contains 10 items and another trial contains only one item and I randomise those, is it guaranteed that the single item of the latter trial is represented as often as each item of the first trial?

2. I always thaught that the randomization of trials in a block leads to a randomization across all trials, but not across the items. In the end, I want the items to be displayed like this for example: Form5, SetA9Y1, Haus7, SetA9Y1, From4, Zahl10, Haus3, Zahl2, SetA9Y1... I do not want a randimization only within the trials, which would look like this Form10, Form2, Form8..., Haus3, Haus9, Haus10...., Zahl2, Zahl5, Zahl1....etc. And that is what I would suspect to happen, if I use your suggestion. Am I wrong? And if not, how can I display the items the way I want them to be displayed?"

You are mixing two things up.

<block primingSetA9Y1>
 /trials = [1-40=noreplacenorepeat(zahl, form, haus, SetA9Y1)]
</block>

The block's /trials attribute determines *how trial elements are sampled*. The above simply means "sample the 4 trial elements zahl, form, haus, and seta9y1 in *equal* proportions", randomly without replacement and avoiding repetitions ("noreplacenorepeat()").

I.e., you are guaranteed to end up with 10 zahl-trials, 10 form-trials, 10 haus-trials, and 10 seta9y1-trials.

How any stimuli *presented* by those trials sample *items* is an entirely different matter. That is determined by the respective *stimulus* element's /select attribute. The default for any stimulus element is to sample its items *randomly without replacement*:

If

<picture formen>
/ items = ("form1.jpg", "form2.jpg", "form3.jpg", ...., "form10.jpg")
/ select = noreplace
</picture>

as presented by

<trial form>
/ stimulusframes = [1=formen]
...
</trial>

has 10 items, and you run the trial 10 times in the block (as per its /trials attribute), each item will be presented once.

If there is only one item as in

<picture seta9y1pic>
/ items = ("seta9y1.jpg")
...
</picture>

as presented by

<trial SetA9Y1>
/ stimulusframes = [1=seta9y1pic]
...
</trial>

and you run that trial 10 times in the block, you'll see that item 10 times.

Given the above, you are indeed wrong regarding

"I do not want a randimization only within the trials, which would look like this Form10, Form2, Form8..., Haus3, Haus9, Haus10...., Zahl2, Zahl5, Zahl1....etc. And that is what I would suspect to happen, if I use your suggestion. Am I wrong?"

This is *not* what you'll get with my suggestion. You will get a random trial-sequence that will look like this

Trial:   Form    SetA9Y1   Haus    SetA9Y1  Form    Zahl      Haus    Zahl... (i.e., no trial-repetitions like Zahl - Zahl or SetA9Y1 - SetA9Y1)
Item:   Form5  SetA9Y1   Haus7 SetA9Y1  Form4  Zahl10 Haus3  Zahl2... (i.e., items sampled randomly w/o replacement)

where each instance of <trial Form> will display a different *item* of <picture formen> (sampled randomly without replacement), and so forth for the other <trial> elements and the respective stimulus elements.

Based on my reading of

"In the end, I want the items to be displayed like this for example: Form5, SetA9Y1, Haus7, SetA9Y1, From4, Zahl10, Haus3, Zahl2, SetA9Y1... "

this should give you exactly what you want.

Edited 6 Years Ago by Dave
mongrel
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Thanks a lot!!! 
You are absolutely right, I was a bit slow there.. :)



mongrel
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Hi again,

now, I am facing the problem the other way around:

I have two trials that I want to be displayed randomly in one block. This time I do not want the items to be displayed equally.
I need the items of the first trial to be randomly displayed 18 times and in-between, I need the stimuli of the second trial to be randomly displayed three times in total. How can I do that?

Thank you in advance!
M.

Dave
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You enter the trials into the selection pool in the desired quantities (this is covered in the documentation for the /trials attribute).

"I need the items of the first trial to be randomly displayed 18 times and in-between, I need the stimuli of the second trial to be randomly displayed three times in total."

means you have a 6:1 ratio. Thus you do:

<block someblock>
/ trials = [1-21 = noreplace(a,a,a,a,a,a,b)]
</block>

This will end up giving you a total of 18 a-trials and 3 b-trials in random order.

Edited 6 Years Ago by Dave
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