On Sat, 20 May 2000 10:08:16 GMT, [EMAIL PROTECTED] (Manni Heumann)
wrote:
>Hi!
>
>We are doing research in visual perception. To measure subjects ability two
>perceive certain stimuli we computed d' or ds. But these measures only provide
>information about the ability to detect one signal.
>We are in the process of designing a new experiment and we would like to know,
>whether subjects can discriminate 3 different stimuli. Unfortunately we do not
>see a way to use signal detection theory here. The problem is, that you can
>tell a hit from some error, but what would be a false alarm?
>Does anyone know of a statistical procedure that would allow us to compute
>one or several indices, that could be used to measure subjects performance?
>Of course this would also influence the question(s) we ask in the experiments
>and probably the number of trials we need per subject and stimulus. But since
>we are still in the design stage, this would not be a great difficulty.
>
>Thanks,
>
>Manni
The question of discriminating among three or more events has been
successfully tackled by Brian Scurfield. He extended typical
two-event ROC analysis to n-event ROC analysis (n>2), where results
are expressed as n-dimentional ROC hypersurfaces, and sensitivity can
be understood in terms of hypervolumes under the hypersurfaces. He
also developed a new type of distribution-free sensitivity measure
based on an information theory analysis of n-event discrimination
tasks. The measure gives an overall measure of detectability among n
events, and also allows sensible comparisons to be made between
n-event tasks and (n-1)-event tasks, say.
Scurfield illustrated his findings using the 3-event case, so if
you're specifically interested in that case, check out his papers:
Scurfield, B.K. (1996) "Multiple-event forced-choice tasks in the
theory of signal detectability", Journal of Mathematical Psychology,
40(3), 253-269
Scurfield, B.K. (1998) "Generalization of the theory of signal
detectability to m-dimensional n-event forced-choice tasks", Journal
of Mathematical Psychology, 42(1), 5-31.
The JMP abstracts used to be available online, but I don't know if
they still are.
Also, there was an independent development of some of this material by
Douglas Mossman. He had a paper in Medical Decision Making in either
1998 or 1999 entitled "Three-way ROCs". Sorry, can't remember the
volume.
Hope this helps,
Vit D.
===========================================================================
This list is open to everyone. Occasionally, less thoughtful
people send inappropriate messages. Please DO NOT COMPLAIN TO
THE POSTMASTER about these messages because the postmaster has no
way of controlling them, and excessive complaints will result in
termination of the list.
For information about this list, including information about the
problem of inappropriate messages and information about how to
unsubscribe, please see the web page at
http://jse.stat.ncsu.edu/
===========================================================================
