Tom, Torben, others -    

Another brief comment on the issue of standardising results reporting, and 
a question:

I think it would help to distinguish: a/ reporting what one’s actually done 
in sufficient detail to allow the analysis to be replicated - essential and 
already what’s expected, even if we aren’t always sure what’s sufficient, 
b/ reporting quality-control of data and analysis, and c/ perhaps allowing 
reviewers &/or, later on, interested readers, to see supplementary data of 
type a/ or type b/ as a matter of course

My question concerns when & how much we should care about residuals that 
don’t wash white. My understanding is roughly:

1 - that in a single-level procedure using a prewhitening approach (e.g. 
SPM2) (I think it’s true of a full ‘mixed-effects’ analysis as well as a 
fixed effects analysis, but correct me if I’m wrong), anything resulting in 
grimy residuals will bias the statistics in favour of over-significance 
i.e. false positives. As bias can be quantified as a proportion (of the 
variance of a true contrast to that of its estimator, see e.g. Friston et 
al 2000, NI), presumably this problem can be quantified for a known effect, 
if we wish. 2 - But, in a two-level random effects (‘summary statistic’) 
procedure such as the one many of us use in SPM2, incorrect prewhitening at 
the 1st level will simply produce less efficient estimators of the true 1st 
level betas and therefore add to the second level contrast variance to a 
relatively small extent

Is this right? This is the kind of reasoning that leads me to think that 
with present procedures including diagnostics of residuals at the first 
level is not necessary (which doesn’t mean it isn’t an important quality 
control tool, and may not become more important if procedures change).

I’d also like to say that the great thing about this kind of discussion is 
that hopefully as well as perhaps producing the guidelines people are 
talking about, the community can find out (in a nice polite fashion!) just 
what it does and doesn’t agree on...

All the best, Alexa PS It seems my fairy (hairy?) godmother put my name on 
the Wiki for me, but I'm pleased to be a part of it!