Randomisation across blocks

[liwenna]

Hey River,

Your question for six days now. Personally I find it hard to see what
could be wrong based on the info given. Could you perhaps post a
screenshot of your setup, make it so that all the relevant lists are
opened and visible, so that the settings are shown (for an example see
this screenshot which was made for another thread ttp://images.redial.net/kkat.bmp).

Or if you have solved problem by now... what was it?

Best regards,

liwenna

On Jun 5, 2:23 pm, River <ll... at medschl.cam.ac.uk> wrote:
> Hi,
>
> I am trying to randomise stimuli across two test blocks using the
> following List settings:
>
> TestBlock1
> 41 random images(unrepeated) from ListA
> 1 cue image_1
> 3 random images (unrepeated) from ListA
>
> TestBlock2
> 41 random images (unrepeated) from ListA
> 1 cue image_2
> 3 random images (unrepeated) from ListA
>
> The random images all come from the same list (BlockListA) with two
> nested lists, Target absent images (containing 43 images)  and Target
> present images(containing 45 images). Each of the two cue images have
> a separate list to themselves.
>
> The TestBlocks state the order should be sequential while BlockListA
> and the Target Absent and Target Present nested lists both state
> ordering should be random (without replacement).
>
> When i run the experiment one of the target absent images is repeated
> instead of showing the final target present image. I can't understand
> why the randomisation is working across these test blocks for all bar
> a single image (not the same one each time)!!
>
> I've changed the experiment to the following structure:
>
> TestBlock1
> 45 (sequentially ordered) images from BlockListA
>
> TestBlock2
> 45 (sequentially ordered) images from BlockListB
>
> Where BlockListA states (sequential ordering):
> 41 images from TargetList (which contains both target absent and
> target present images)
> 1 image from Cue_1
> 3 images from TargetList
>
> Where BlockListB states (sequential ordering):
> 41 images from TargetList (which contains both target absent and
> target present images)
> 1 image from Cue_2
> 3 images from TargetList
>
> Where TargetList ordering is random without replacement. This seems to
> work (i've run the experiment 8 times so far with no duplicates/
> missing images) but i'd like to know why this would work instead of
> the above described experiment as essentially the only difference is
> that the random images are all in the same list and the sequential
> ordering of 41 random images, 1cue, 3 random images is described later
> on in the list structure (i.e. in BlockListA not TestBlock).
>
> I hope this is clear enough! Any advice would be much appreciated.
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