Trouble with randomisaton

[David McFarlane]

Laura,

I am stumped on this one.  First thing I would do is to set this back 
to Sequential order and run a bunch of tests that way.  For these 
tests I would also use names like 01.jpg, etc., just to make it 
easier to read.  Finally, don't neglect PST Web Support at 
http://support.pstnet.com/e%2Dprime/support/login.asp .  they strive 
to respond to all requests in 24-48 hours (although current estimates 
are more like 10 days) -- this is pretty much their substitute for 
proper documentation, so make full use of it.  And please do write 
back when/if you get this sorted out.

-- David McFarlane, Professional Faultfinder


At 6/22/2010 07:42 PM Tuesday, Little Moo wrote:
>I'm hoping someone can help.
>
>Has anyone else had a problem with randomisation, or am I doing
>something wrong.
>
>In the final phase of an experiment, I have a list of 27 target
>images, and 3 lists of distractor images.
>
>The list is set as:-
>
>27 Samples (1 cycle x 27 samples/cycle)
>
>1 Cycle equals 27 samples
>
>Random Selection
>
>In a small, but significant, number of experimental runs, one level is
>omitted and one level is repeated e.g.
>
>red_squr_straight.jpg
>blck_tri_squig.jpg <------------First Show
>blue_tri_round.jpg
>blue_tri_straight.jpg
>red_circ_straight.jpg
>red_squr_squig.jpg
>blue_squr_squig.jpg
>red_tri_round.jpg
>blue_circ_squig.jpg
>blue_circ_straight.jpg
>blck_squr_round.jpg
>blue_tri_squig.jpg
>red_squr_squig.jpg
>blck_circ_round.jpg
>blck_tri_squig.jpg <------------Repeated
>blck_circ_straight.jpg
>blue_squr_straight.jpg
>red_tri_squig.jpg
>red_tri_straight.jpg
>red_squr_round.jpg
>blue_tri_squig.jpg
>blue_squr_round.jpg
>blck_tri_straight.jpg
>blue_circ_round.jpg
>blue_tri_straight.jpg
>blck_squr_straight.jpg
>red_tri_squig.jpg
>
>and in this case blck_circ_squig.jpg was omitted - that is for this
>case only, the level omitted/repeated is random.
>
>Has any else noticed this, or have I made a mistake with my selection
>criteria? Reset is set to All samples (27), and the list object does
>have 27 unique filenames.
>
>This is central to my experiment but nothing I have tried works.
>
>Laura

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