Subject: Re: Experiments with large N From: Massimo Grassi <massimo.grassi@xxxxxxxx> Date: Tue, 4 Dec 2007 09:37:24 +0100 List-Archive:<http://lists.mcgill.ca/scripts/wa.exe?LIST=AUDITORY>Dear all, > Huge samples are very nice if you can get 'em, though such is not always > the case, alas. snip! If I had a large (very large) N I would be more interested in have a glance of the population distribution. And this is the reason why, I think, large N studies are important. For example, last year Semal and Demany (JASA, 2006) showed that there are listerers that are able to detect subtle pitch differences but, at the same time, are not able to tell the direction of these pitch differences (up or down). They showed also that there are listeners that do not show such a dissociation. How is the distribution of this trait among the population? Are the first listeners a small or a relatively large amount of the population? Think about. Pitch perception is one of the most investigated topic in auditory perception. Why do we discover this only in 2006? Is it because the average study is run with few listeners only and these listeners are, in the majority of cases, the "usual suspects" (e.g., authors, people with a background of a minimum of 1000 hours of psycho-beeps experiment, etc.). In textbooks we often read that JND for pitch is about 1%. After reading Semal and Demany results I asked myself: is this figure real? Does it reflect all the population? Which part of the population? For which particular task? It is trivial to stress that, with large N, statistical power goes soon very high. I think the goal of large N study is different: have, at least once, a real glance of the population. m -- Massimo Grassi - PhD Dipartimento di Psicologia Generale Via Venezia 8 - 35131 Padova - Italy http://www.psy.unipd.it/~grassi http://percezione.wordpress.com/