How do I make sure that stimuli are only presented once?


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Shona
Shona
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Posts: 72, Visits: 58

Hello, 


I would like to present each image and question one time over the course of my survey. Right now, my script chooses images and questions randomly each time so that there is some repetition of certain stimuli and others are never presented. 


How do I fix this problem?


My script is pasted below and I'd be so grateful for any help!


Shona



***************************** Stimuli ********************************



Neutral 


<item targetN> 


/1= "Neut_7175.jpg"


/2= "Neut_2440.jpg"


/3= "Neut_2480.jpg"


/4= "Neut_7060.jpg"


/5= "Neut_7110.jpg"



</item>



High Pleasure 


<item targetHP>


/1= "HP_4290.jpg"


/2= "HP_4608.jpg"


/3= "HP_8185.jpg"


/4= "HP_8186.jpg"


/5= "HP_8370.jpg"



</item>



High Threat 


<item targetHT>


/1= "HT_6230.jpg"


/2= "HT_6370.jpg"


/3= "HT_6550.jpg"


/4= "HT_9250.jpg"


/5= "HT_1300.jpg"



</item>



Mildpleasure 


<item targetMP>


/1= "MP_2310.jpg"


/2= "MP_5220.jpg"


/3= "MP_1600.jpg"


/4= "MP_2222.jpg"


/5= "MP_5780.jpg"



</item>



Mildthreat


<item targetMT>


/1= "MT_2750.jpg"


/2= "MT_2276.jpg"


/3= "MT_9265.jpg"


/4= "MT_9000.jpg"


/5= "MT_2590.jpg"



</item>




<text textquestions>


/size = (45%, 45%)


/items = textquestions


/position = (50%, 50%)


/halign = center


/select = noreplacenorepeat


/selectionrate = always


</text>




<item textquestions>


/1= "Death penalty."


/2= "Multiculturalism."


/3= "Stiffer jail terms."


/4= "Patriotisim."


/5= "Voluntary euthanasia."


/6= "Nuclear power."


/7= "Working mothers."


/8= "Bible truths."


/9= "Gay rights."


/10= "Conservationalists."


/11= "Sabbath observance."


/12= "Royalty."


/13= "Test-tube babies."


/14= "Pre-marital virginity."


/15= "Asian immigration."


/16= "Decriminalised marijuana."


/17= "Church authority."


/18= "Defense spending."


/19= "Legalised abortion."


/20= "Caning young criminals."


/21= "Private schools."


/22="Condom vending machines."


/23= "Legalised prostitution."


/24= "Castrating sex offenders."


/25= "Women priests."



</item>



<shape erasescreen>



/color= (255,255,255)


/size = (100%, 100%)



</shape>



************************** Experimental Stimuli ************************************



<picture targetN>


/ items = targetN


/ size = (40%, 40%)


/ position = (50%,50%)


/ select = mycounter1 


/ selectionrate = always


</picture>



<picture targetHP>


/ items = targetHP


/ size = (40%, 40%)


/ position = (50%,50%)


/ select = mycounter2


/ selectionrate = always


</picture>



<picture targetHT>


/ items = targetHT


/ size = (40%, 40%)


/ position = (50%,50%)


/ select = mycounter3


/ selectionrate = always


</picture>



<picture targetMP>


/ items = targetMP


/ size = (40%, 40%)


/ position = (50%,50%)


/ select = mycounter4 


/ selectionrate = always


</picture>



<picture targetMT>


/ items = targetMT


/ size = (40%, 40%)


/ position = (50%,50%)


/ select = mycounter5


/ selectionrate = always


</picture>



*************************** Picture Trials *********************************



Neutral Trial 


<trial targetN>


/stimulusframes = [1=targetN; 250=erasescreen]


/response = timeout(250)


</trial>



High Positive Trial 


<trial targetHP>


/stimulusframes = [1=targetHP; 250=erasescreen]


/response = timeout(250)


</trial>



High Threat Trial


<trial targetHT>


/stimulusframes = [1=targetHT; 250=erasescreen]


/response = timeout(250)


</trial>



Mild Positive Trial 


<trial targetMP>


/stimulusframes = [1=targetMP; 250=erasescreen]


/response = timeout(250)


</trial>



Mild Threat Trial 


<trial targetMT>


/stimulusframes = [1=targetMT; 250=erasescreen]


/response = timeout(250)


</trial>



*************************** Likert **********************************



<likert likert1>


/ anchors = [1= "Against"; 2= "2" , 3 = "3" , 4 = "4" , 5 = "5" , 6 = "6" , 7 = "For"]


/ numpoints = 7


/ stimulusframes = [1 = textquestions]


/ position = (50%,90%)


/ anchorwidth = 5%


/ fontstyle = ("Verdana", 8pt , true)


/ mouse=false


/ numpoints= 7


</likert>




************************** Blocks ***************************************



<block myblock>


/ trials = [1,3,5,7,9,11,13,15,17,19,21,23,25,27,29,31,33,35,37,39,41,43,45,47,49=noreplacenorepeat(targetMT, targetHT, targetMP, targetHP); 2,4,6,8,10,12,14,16,18,20,22,24,26,28,30,32,34,36,38,40,42,44,46,48,50=noreplacenorepeat(likert1)]


</block>





********************************** Counter **********************************



<counter mycounter1>


/ select = noreplacenorepeat (1-5)


/ selectionrate = always


/allowrepeats=false


</counter>



<counter mycounter2>


/ select = noreplacenorepeat (1-5)


/ selectionrate = always


/allowrepeats=false


</counter>



<counter mycounter3>


/ select = noreplacenorepeat (1-5)


/ selectionrate = always


/allowrepeats=false


</counter>



<counter mycounter4>


/ select = noreplacenorepeat (1-5)


/ selectionrate = always


/allowrepeats=false


</counter>



<counter mycounter5>


/ select = noreplacenorepeat (1-5)


/ selectionrate = always


/allowrepeats=false


</counter>




************************** Experiment *************************************



<expt>



/preinstructions = (test)


/blocks = [1= myblock]


/postinstructions= (end)



</expt>




************************* Intructions **************************************



<instruct> 


/nextlabel= "press the spacebar to proceed"


/lastlabel= "Press the spacebar to proceed"


/nextkey = (" ")


/fontstyle = ("Arial", 2%. false , false , false , false, 5, 0)


</instruct>



<page test>



In the next phase of the experiment, you will be presented with images and asked questions about your political beliefs. On each of the 25 trials, you will be shown an image for 3 seconds and then asked to indicate on a 1-7 scale, the extent to which you are 'for' or 'against' a given political issue. Please answer these questions as honestly as possible. 



</page>



<page end>



Please proceed to the next phase of the experiment. 



</page>




Dave
Dave
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Posts: 10K, Visits: 58K

You need to start thinking about sampling more carefully.


/ trials = [1,3,5,7,9,11,13,15,17,19,21,23,25,27,29,31,33,35,37,39,41,43,45,47,49=noreplacenorepeat(targetMT, targetHT, targetMP, targetHP);


... means you are trying to sample 25 times from a pool consisting of 4 elements in equal proportions. 25/4 = 6,25, so obviously the math does not check out. Effectively, every element will be available 7 times in the pool, giving it a size of 4*7=28. Out of those 28, only 25 will be sampled, some more than others. It also seems you've forgotten about your neutral <trial targetN> here.



Lots of other stuff in your script does not make sense either and may cause problems. For example:


<counter mycounter1>
/ select = noreplacenorepeat (1-5)
/ selectionrate = always
/ allowrepeats=false
</counter>


Ask yourself: What's the point in sampling from 5 *different* values (1, 2, 3, 4 and 5) without replacement *and without repetition*? They are different, so there could not possibly be any repeats. You should go for straight noreplace().


Furthermore, why use /selectionrate=always when -- judging from your script -- you only want *a single* sample from the pool per <trial>? You should go for the default /selectionrate=trial.


For some reason, you use the <counter> elements to determine selection for your <picture> elements:


<picture targetN>
/ items = targetN
/ size = (40%, 40%)
/ position = (50%,50%)
/ select = mycounter1
/ selectionrate = always
</picture>


(a) Why?


(b) /selectionrate is already determined by the <counter> and is thus redundant and ineffective here.


(c) Again: Why selectionrate=always?


You can throw away all the useless counters a simplify to


<picture targetN>
/ items = targetN
/ size = (40%, 40%)
/ position = (50%,50%)
/ select = noreplace
</picture>


etc.


All of the above also applies to your <text> element(s).


GO

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