For those who are interested in reading the Margulies chapter that Jeff cites below, most of if is accessible on books.google.com at: http://books.google.com/books?hl=en&lr=&id=qp1NUVdlcZAC&oi=fnd&pg=PA273&dq=Margulies,+D.+S.+%282011%29+The+salmon+of+doubt:+Six+months+of+methodological++controversy+within+social+neuroscience.+&ots=FfQRwOrz7a&sig=yrKiZWtkxyQPjDeGxA1nn6piFGo#v=onepage&q&f=false
However, it is not clear from this source whether the correct "correction" was applied or not. The issue is comparable to that of multiple comparison testing after a significant F in an ANOVA (NOTE: I assume that the corrections were planned before the data was collected and not after one has looked at the data or that one is engaged in unplanned comparisons). The Bonferroni correction is one way to do it but there are others; see, for example, the following: http://jeb.sagepub.com/content/5/3/269.short Now, I'm not familiar with what kind of voodoo, er, I mean, statistical rituals they follow in analyzing neuroimaging data, whether they test for homogeneity of variance, sphericity, or other conditions necessary the validity of the statistical tests they do. I see no argument provided for why the Bonferroni procedure was used instead of other procedures, such as: http://biomet.oxfordjournals.org/content/73/3/751.short or Multiple Comparison Methods for MeansAuthor(s): John A. Rafter, Martha L. Abell and James P. Braselton Source: SIAM Review, Vol. 44, No. 2 (Jun., 2002), pp. 259-278 Published by: Society for Industrial and Applied Mathematics Stable URL: http://www.jstor.org/stable/4148355 . NOTE: This presentation assumes that the means are independent; within-subject designs produced correlated results and complicate things. So, when it comes to correcting for the number of tests one is doing, there's more than one way to skin a cat or prepare a salmon. And let's not even get started on the reduction of power in making the correction. -Mike Palij New York University [email protected] ---------------------- Original Message ---------------------------------- On Wed, 11 Jul 2012 17:13:41 -0700, Jeffry Ricker, PhD wrote: On Jul 11, 2012, at 6:33 AM, Marc Carter wrote: > Only offering this as a cautionary tale (but not taking sides because others > know far more about this than I), and because it's damned funny. > http://prefrontal.org/files/posters/Bennett-Salmon-2009.pdf > I always use this in my methods and cognitive classes to make sure that > students don't jump to conclusions. And they get a big laugh out of it, as I > did. I don't think the authors meant it as a cautionary tale. According to Margulies (2011), the poster was intended to be a light-hearted demonstration that the statistical corrections typically used by social-neuroscience researchers are generally adequate for validly interpreting fMRI results: >> Before proper correction for multiple comparisons, a cluster 27 mm3 was >> found to be significant within the brain cavity; however, the authors >> dutifully noted that “due to the coarse resolution of the echo-planar image >> acquisition and the relatively small size of the salmon brain further >> discrimination between brain regions could not be completed” (Bennett et >> al., 2009). Of course (and thankfully), after proper statistical >> correction, no active voxels were detected. (emphasis added, p. 282) Margulies continued: >> To those unfamiliar with the techniques, this appeared to be another >> successful attack against social neuroscience.... However, those within the >> community understood that the obvious tongue-in-cheek presentation was far >> from being an attempt to invalidate fMRI approaches to questions of social >> cognition. Rather, it was an example of statistical criticism, which >> reinforced the validity of correction techniques that have long been argued >> as essential. (pp. 282-283) Best, Jeff Margulies, D. S. (2011) The salmon of doubt: Six months of methodological controversy within social neuroscience. In S. Choudhury & J. Slaby (Eds.), Critical Neuroscience: A Handbook of the Social and Cultural Contexts of Neuroscience (pp. 273-285). London: Wiley-Blackwell. doi: 10.1002/9781444343359.ch13 --- You are currently subscribed to tips as: [email protected]. To unsubscribe click here: http://fsulist.frostburg.edu/u?id=13090.68da6e6e5325aa33287ff385b70df5d5&n=T&l=tips&o=18969 or send a blank email to leave-18969-13090.68da6e6e5325aa33287ff385b70df...@fsulist.frostburg.edu
