Re: Experiments with large N

[Massimo Grassi <massimo.grassi@xxxxxxxx>]

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/