Millisecond Online Community

Hi All,

We have created a ST-IAT with one practice block and two test blocks for our experiment. We are already able to run the program, but we think there is something wrong with the scoring. However, every time we take the test, the scoring turns out to be zero (regardless of the amount of mistakes and/or reaction times). Is there anybody who can help us?

Lieke & Eline

Hi Lieke & Eline,

without actually having your script at hand, that question is really hard to answer. So, I assume that you've modified an existing script for the ST-IAT, i.e. the one available at this site. The scoring routine might have been affected by removing the blocks it relies on. In the original, the scoring magic happens here:

***********************************************************************
Scoring
***********************************************************************
<values>
/ sum1a = 0
/ sum2a = 0
/ sum1b = 0
/ sum2b = 0
/ n1a = 0
/ n2a = 0
/ n1b = 0
/ n2b = 0
/ ss1a = 0
/ ss2a = 0
/ ss1b = 0
/ ss2b = 0
/ magnitude = "unknown"
</values>

* 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
/ attitude = "unknown"
</expressions>

At the beginning, all values are initialized as 0. This is probably why you always get 0 as your result in the adapted script. The values are updated by the /ontrialend attributes of the <block> elements. Clearly, the final d-value is computed from results from 2 compatible and 2 incompatible blocks. You only have 1 compatible and 1 incompatible block. So, you'll simply have to adapt the scoring to your modified procedure in order to make it work correctly.

Hope this gives you a starting point.
~Dave