Hello everyone,
I am not sure whether this belongs into the Millisecond Community at all and I have checked out the other post about IAT reliabilities but it is not helping me.
I carried out an ST-IAT with a script from the download area (based on Blümke & Friese, 2008) and now I want to calculate its reliability.
Blümke & Friese calculate Cronbach's alpha for their ST-IAT: "We calculated Cronbach’s a based on a full 34-item scale of trial-wise latency-differences (with missing data being
replaced by participants’ mean latencies, i.e. a z-score of zero."
Schnabel, Asendorpf and Greenwald (2007) say about the IAT: "There exist various ways for calculating internal consistencies of IAT D measures. Some
compute difference scores for every single trial of the combined blocks and treat them as
separate items to calculate Cronbach’s internal consistency alpha, some employ difference
scores for blocks of 5, 10, 20 or more trials, some calculate split-half reliabilities over blocks
with identical number of trials, and some over blocks with different numbers of trials."
I am a Master's student and am doing this on my own and with no experience in reaction time research. I don't know if I am being really dense, but I really don't understand what exactly it is they are doing.
e.g. "trial-wise latency-differences" - do they mean calculate the latency difference between the 3rd trial of block 1 (motiv + positive) and the 3rd trial of block 2 (motive + negative)? Would I have to make sure it's the same kind of trial (trial order is not identical between blocks)?
And for split-half: some use odd vs. even numbered trials and correlate the D-scores. Does this mean I calculate a D-score for all even numbered trials and a separate one for all odd numbered trials of one block pair? That would make sense to me, though I would still be a bit worried about whether roughly equal numbers of the same trial kind were included in both.
Can anyone walk me through it?