SC-IAT Scoring


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becgwin
becgwin
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Hi,

I ran an SC-IAT last year based on the Inquisit task library version dated 03-26-2013 and I am slightly confused by the summary output. While I get no expressions.da (it appears to leave out calculations of the practice trials), I do get an expressions.db (which according to previous posts is for the test trials - topics3444) and an expressions.d (which according to same post is meant to combine practice and test trials). The expressions.d seems to be the expressions.da divided by 2. The expressions.latdiffb and expressions.latdiff are identical which I think makes sense if the practice trials are not included. I have since seen the updated version of the SC-IAT (dated 11-21-2013) and the programmed output makes more sense to me, so I assume it may have been amended in part to address this issue.  I just want to confirm that expressions.db in my summary output is D for test trials, and what I should use assuming I am satisfied to exclude trials larger than 10000ms and error trials.  Also, can anyone explain what expressions.d is in this case when it appears the practice trials were not included in the analysis, and yet it differs from expressionsdb. The script is as follows:

* 1 is compatible, 2 is incompatible
* a is first block, b is second block

<expressions>
/ m1a = values.sum1a / values.n1a
/ m2a = values.sum2a / values.n2a
/ m1b = values.sum1b / values.n1b
/ m2b = values.sum2b / values.n2b
/ sd1a = sqrt((values.ss1a - (values.n1a * (expressions.m1a * expressions.m1a))) / (values.n1a - 1))
/ sd2a = sqrt((values.ss2a - (values.n2a * (expressions.m2a * expressions.m2a))) / (values.n2a - 1))
/ sd1b = sqrt((values.ss1b - (values.n1b * (expressions.m1b * expressions.m1b))) / (values.n1b - 1))
/ sd2b = sqrt((values.ss2b - (values.n2b * (expressions.m2b * expressions.m2b))) / (values.n2b - 1))
/ sda = sqrt((((values.n1a - 1) * (expressions.sd1a * expressions.sd1a) + (values.n2a - 1) * (expressions.sd2a * expressions.sd2a)) + ((values.n1a + values.n2a) * ((expressions.m1a - expressions.m2a) * (expressions.m1a - expressions.m2a)) / 4) ) / (values.n1a + values.n2a - 1) )
/ sdb = sqrt((((values.n1b - 1) * (expressions.sd1b * expressions.sd1b) + (values.n2b - 1) * (expressions.sd2b * expressions.sd2b)) + ((values.n1b + values.n2b) * ((expressions.m1b - expressions.m2b) * (expressions.m1b - expressions.m2b)) / 4) ) / (values.n1b + values.n2b - 1) )
/ da = (m2a - m1a) / expressions.sda
/ db = (m2b - m1b) / expressions.sdb
/ d = (expressions.da + expressions.db) / 2
/ latdiffa = m2a - m1a
/ latdiffb = m2b - m1b
/ latdiff = ((values.sum2a + values.sum2b) / (values.n2a + values.n2b)) - ((values.sum1a + values.sum1b) / (values.n1a + values.n1b))
/ attitude = "unknown"
</expressions>


Finally, can any-one confirm that the raw error trial latencies are uncorrected, or corrected for in calculations only by their exclusion?  That way I can easily run my own analysis if I want to change the parameters e.g. delete trails less than 350ms etc.

Thanks,

Rebecca 








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                         Hi again, for what I think its the final time. Surprisingly I seem to...
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